Case insensitive installed file lookup on Windows

[HebaruSan]

Problems

Recently, Windows users have been encountering weird install/uninstall errors relating to Scatterer:

Causes

In its latest release, Scatterer renamed its install folder from scatterer to Scatterer (capitalizing the S), but the metadata was unchanged until KSP-CKAN/NetKAN#8862. There was no inflation error because install stanza matching is case insensitive, so find: scatterer matched a path in the ZIP of Scatterer:

CKAN/Core/Types/ModuleInstallDescriptor.cs

Lines 230 to 245 in 35927bc

	{
	file = CKANPathUtils.NormalizePath(file);
	inst_pattern = new Regex(@"^" + Regex.Escape(file) + @"(/|$)",
	RegexOptions.IgnoreCase | RegexOptions.Compiled);
	}
	else if (find != null)
	{
	find = CKANPathUtils.NormalizePath(find);
	inst_pattern = new Regex(@"(?:^|/)" + Regex.Escape(find) + @"(/|$)",
	RegexOptions.IgnoreCase | RegexOptions.Compiled);
	}
	else if (find_regexp != null)
	{
	inst_pattern = new Regex(find_regexp,
	RegexOptions.IgnoreCase | RegexOptions.Compiled);
	}

One user who encountered these errors shared a screenshot confirming that the mod was installed into GameData/scatterer:

But their registry.json has it as GameData/Scatterer in the installed_files hashes:

https://1drv.ms/u/s!AlCbO5GR6RGwj7RlQn2vSUdicVFNQA?e=pJQfMM

On Windows, filenames are treated as case insensitive, so if we take a filename with mismatched capitalization from the registry and look for it on disk, it will be found. But Dictionary<string, whatever> lookups are case sensitive by default, so if we take a filename with mismatched capitalization from disk and look for it in the registry, it won't be found unless we take extra steps to make that happen.

One place this happens is when we look for manually installed DLLs. This is done by iterating over all the DLLs in GameData and checking whether each one is registered to an installed module. If the capitalization is mismatched, then that code does not find the file and adds it to the list of manually installed DLLs. Later the RelationshipResolver will trip on Scatterer's self-conflict when it sees it in the manually installed DLL list and emit the above strange errors.

Changes

Now on Windows we initialize the installed_file dictionaries with StringComparer.OrdinalIgnoreCase, which makes their key lookup case insensitive. This should allow us to find files properly when going from disk to the registry, so CKAN will no longer think that Scatterer.dll is manually installed.

[DasSkelett]

Did some testing on Windows now, both the metadata changes and this PR solve it on their own, i.e. either updating the metadata or using the updated client are enough to mitigate it, both together obviously works as well.
And I realized that there were more Scatterer releases since the folder name changed, but they have been deleted from SpaceDock. So I'll do some backporting of KSP-CKAN/NetKAN#8862 just to be safe

[HebaruSan]

both the metadata changes and this PR solve it on their own, i.e. either updating the metadata or using the updated client are enough to mitigate it

Excellent news, that means we don't need to rush the next release. 👍