Localize strings on `github.dev`

[karrtikr]

Change localization in the extension to use async VS Code FS APIs, as native node fs APIs are not available in browser. Some work done here: #17711

[karrtikr]

Converting the existing localize module to async is a problem as that means we cannot load any existing localized strings at module level in the extension. Two approaches:

• Fix all localized constants in the extension to not be imported at module level.
• Create a separate localization module for the browser case which used the VSCode API.

If first approach seems to take a long time, we should be going with the second approach.