make "open terminal here" context menu work for directory background

[hereafter]

This commit makes "Open in Windows Terminal" Context menu work again for
directory background even on system that OS fix is not applied.

This is a fallback solution to OS fixes mentioned in #6414.
While OS fix is on its way, we need a fallback that works on existing OS
versions.

The approach to this is: when no item is selected (nullptr for
IShellItemArray*), we use shell api to query the path of current active
Explorer window. A special case is handled for Windows Desktop. Once
we are able to obtain the path, we launch Windows Terminal with it.

Validation Steps Performed

1. Right click on desktop to bring up the Context menu, pick "Open in
   Windows Terminal", verify that a terminal is opened with correct
   initial path.

2. Open a few File Explorer windows, pick any window, navigate to a
   folder, click on "Background" to bring up the context menu, click
   "Open in Windows Terminal" verify that a terminal is opened with
   correct initial path.

Closes #6414

[github-actions]

New misspellings found, please review:

• CSIDL
• IDispatch
• IWeb
• Progman
• SHANDLE
• SHGFP
• WClass

To accept these changes, run the following commands

perl -e '
my @expect_files=qw('".github/actions/spell-check/expect/5757ec679b03a4240130c3c53766c91bbc5cd6a7.txt
.github/actions/spell-check/expect/655f007265b351e140d20b3976792523ad689241.txt
.github/actions/spell-check/expect/alphabet.txt
.github/actions/spell-check/expect/expect.txt
.github/actions/spell-check/expect/web.txt"');
@ARGV=@expect_files;
my @stale=qw('"AAAAA Bopomofo Checkboxes CParams cso CSV DOWNSCALE GENERATEPROJECTPRIFILE hhhh Horiz Inlines INPATHROOT intersectors Kode MAKEINTRESOURCEA mousemode msixbundle psin Reserialize reso RETROII rgus sbri scanbri scol SGRXY spe sph spherefunctions tcon UDK UDKs Unfocus Viginetting wz xe xlang XWV xyw yzx "');
my $re=join "|", @stale;
my $suffix=".".time();
my $previous="";
sub maybe_unlink { unlink($_[0]) if $_[0]; }
while (<>) {
  if ($ARGV ne $old_argv) { maybe_unlink($previous); $previous="$ARGV$suffix"; rename($ARGV, $previous); open(ARGV_OUT, ">$ARGV"); select(ARGV_OUT); $old_argv = $ARGV; }
  next if /^($re)(?:$| .*)/; print;
}; maybe_unlink($previous);'
perl -e '
my $new_expect_file=".github/actions/spell-check/expect/a129ff14ec985d6b7bf09e296a831c955d41040b.txt";
open FILE, q{<}, $new_expect_file; chomp(my @words = <FILE>); close FILE;
my @add=qw('"checkboxes CSIDL csv horiz IDispatch inlines IWeb Progman reserialize SHANDLE SHGFP udk unfocus WClass "');
my %items; @items{@words} = @words x (1); @items{@add} = @add x (1);
@words = sort {lc($a) cmp lc($b)} keys %items;
open FILE, q{>}, $new_expect_file; for my $word (@words) { print FILE "$word\n" if $word =~ /\w/; };
close FILE;'
git add .github/actions/spell-check/expect || echo '... you want to ensure .github/actions/spell-check/expect/a129ff14ec985d6b7bf09e296a831c955d41040b.txt is added to your repository...'

✏️ Contributor please read this

By default the command suggestion will generate a file named based on your commit. That's generally ok as long as you add the file to your commit. Someone can reorganize it later.

⚠️ The command is written for posix shells. You can copy the contents of each perl command excluding the outer ' marks and dropping any '"/"' quotation mark pairs into a file and then run perl file.pl from the root of the repository to run the code. Alternatively, you can manually insert the items...

If the listed items are:

• ... misspelled, then please correct them instead of using the command.
• ... names, please add them to .github/actions/spell-check/dictionary/names.txt.
• ... APIs, you can add them to a file in .github/actions/spell-check/dictionary/.
• ... just things you're using, please add them to an appropriate file in .github/actions/spell-check/expect/.
• ... tokens you only need in one place and shouldn't generally be used, you can add an item in an appropriate file in .github/actions/spell-check/patterns/.

See the README.md in each directory for more information.

🔬 You can test your commits without appending to a PR by creating a new branch with that extra change and pushing it to your fork. The :check-spelling action will run in response to your push -- it doesn't require an open pull request. By using such a branch, you can limit the number of typos your peers see you make. 😉

⚠️ Reviewers

At present, the action that triggered this message will not show its ❌ in this PR unless the branch is within this repository.
Thus, you should make sure that this comment has been addressed before encouraging the merge bot to merge this PR.

[DHowett]

WOW! This is clever!

[carlos-zamora]

Requesting some minor changes. This is awesome though, thanks!

[zadjii-msft]

Okay, I love how clever this is. I've got a bunch of basically nits, but largely this seems good to me. Thanks!

[DHowett]

You will need to update the other two appxmanifest files in the src/Cascadia/CascadiaPackage directory. They are used for the Release and Preview versions!

[fxzxmic]

Awaiting!! It would be better if the right-click menu option had localization.

[DHowett]

I've chatted with the team who owns explorer shell extensions, and they have conceded that they will accept this workaround. Thanks so much, this is a very clever solution. I love it.

[ghost]

Hello @DHowett!

Because this pull request has the AutoMerge label, I will be glad to assist with helping to merge this pull request once all check-in policies pass.

p.s. you can customize the way I help with merging this pull request, such as holding this pull request until a specific person approves. Simply @mention me (@msftbot) and give me an instruction to get started! Learn more here.

[hereafter]

Awesome :) glad it helps.

[ghost]

🎉Windows Terminal v1.5.10271.0 has been released which incorporates this pull request.:tada:

Handy links:

• Release Notes
• Store Download

[ghost]

🎉Windows Terminal Preview v1.6.10272.0 has been released which incorporates this pull request.:tada:

Handy links:

• Release Notes
• Store Download