Adopt codicons for bundled extensions

[KamasamaK]

With #84695 and related issues deployed, bundled extensions like npm and git can replace most of their bundled svg icons with native codicons.

[miguelsolorio]

Moving the discussion from using codicons in file icons to #91973 as this issue is specific to our bundled extensions.

[KamasamaK]

Looking over the two example bundled extensions, I've found a couple limitations that would prevent completely replacing with codicons.

• For npm, the prepostscript.svg cannot be replaced because codicons do not have adjustable opacity.
• For git, none of the status-*.svg have equivalent codicons.

[miguelsolorio]

@KamasamaK I'm working on updating these two extensions and will address those two issue.

[KamasamaK]

Just to be complete, even though I only mention those two examples there's also markdown-language-features and possibly image-preview that could use this treatment.

[miguelsolorio]

This is already done. The markdown extension has been updated (we still need the preview icon since codicons aren't supported there) and the image preview is a webview.

[KamasamaK]

Thanks. I see #99976 was opened for the Markdown extension.