GH-587: Negative integer short values

[FrankRay78]

This is a rebased version of an existing PR, namely #732 ("Fixes #587 Support negative numbers as command option values") which was created on 16 Feb 2022 and is now 94 commits behind main.

Some of the conflicts arising from the rebase required manual fixing as directories had been deleted / relocated.

I am submitting this updated PR directly here (and not in addition to the original PR) because I am not authorised to push to jouniheikniemi's original branch.

Additionally, I've addressed @phil-scott-78 's previous review comment:

But think we could get some tests that cover the invalid cases as described in the comments of the tokenizer for invalid items?

And made some minor stylistic updates of my own to largely keep the code base consistent, arising from my review comments I left on the earlier PR.

[FrankRay78]

ℹ️ Note ℹ️ - The following three PR's, when taken jointly, represent a significant enhancement to existing command line parsing behaviour: #1036, #1029, #1040

However, they all make changes to CommandTreeTokenizer and introduce their own unit tests specifically for the CommandTreeTokenizer, and as such, merge conflicts will arise once any one of the PR's has been merged.

I plan to merge all three PR's onto a single local branch to examine the extent of the conflicts, and hopefully resolve them as I go. It might be prudent to consider waiting and then merging this resolved, single branch @patriksvensson, rather than the 3 separate PR's mentioned above.

[patriksvensson]

@FrankRay78 Whatever works best for you! Planning on sitting down this week and look through your work. A lot of nice changes!

[FrankRay78]

@FrankRay78 Whatever works best for you! Planning on sitting down this week and look through your work. A lot of nice changes!

I recommend waiting for the consolidated branch - I'm right in the middle of merging it now and it will be done in the next day or two. I'm also squashing the various commits in each previous PR so it's easier to see the changes. It's taken me a little while to get to grips with git properly, apologies for the amateur PR's previously...

[FrankRay78]

Closing as superseded by #1048