Use product icons instead of 'hardcoded' icons

[DeltaRazero]

This changes themability

The following changes are proposed/purpose of the changes:

• Add a product icon font instead of 'hardcoded' icons. This has the following benefits:
  • Product icon themes can now override the icons if desired
  • Color themes can now properly set the colors of the icons, so no need to maintain light and dark icons that are not following the theme's colors.
• Add a script using FontForge scripting API for generating product icon font for future use
  • I feel like FontForge is a good cross-platform open source platform to use as font generator. It is robust and it doesn't require a separate installation of Python to invoke the scripting API (i.e. FontForge bundles its own Python runtime).
  • The inclusion of the script is purely for future use if more icons are needed
  • Filenames of icons now include the glyph codepoint so it's easier to see what the codepoint is for each icon, as well as the script uses this for mapping the icons to the desired codepoints.
• Remove redundant icons that are already part of codicons; change the package.json to use the already present codicons

Furthermore, I centered the build icon as it was off-center.

[DeltaRazero]

@microsoft-github-policy-service agree

[DeltaRazero]

@gcampbell-msft Could you kindly provide me with feedback or a comment please? Thanks!