Fix language-map.json build script

[zm-cttae]

• Search for extension manifests in microsoft/vscode instead of microsoft (half the manifests, more languages).
• Add logic to try match contributed filenames/extensions to their icon using the existing icon map.
• Abstract the icon name logic in the build script.

Test case:

• v1.7.3 will throw an error in processLanguageContribution because lang isn't reassigned back
• https://github.com/microsoft/vscode/blob/1.74.0/extensions/shellscript/package.json#L28-L69 Once fixed and run, any matches to console will disappear in language-map.json

[Claudiohbsantos]

@zm-cttae I know I'm already a couple of months late but just wanted to bump this PR so you see that I saw it. I will need to dig a little bit into what these changes would mean so it'll take me a little bit to have a proper review but overall I'm not against these changes.

[zm-cttae]

Cool. The big change is https://github.com/Claudiohbsantos/github-material-icons-extension/pull/49#discussion_r1045286088 which brings us closer to the upstream extension in behaviour