All of the interactions with `pygmentize` have been refactored into a
new class, conviently called Pygmentize. It is responsible for getting
* pygments version (cached in APCu for 1 hour)
* generated CSS (cached in WAN by version for 1 week)
* lexer list (cached in APCu by version for 1 day)
and actually highlighting stuff! Most code paths differentiate whether
we're using a bundled version of pygments or one that has been
explicitly configured. If using the bundled one, we take shortcuts since
we already know the lexer list, have the CSS generated, etc.
ResourceLoaderPygmentsModule is added to switch between loading
generated CSS from the bundled file or Shellboxing out to get it from
pygments.
Bug: T289227
Change-Id: I2e82e5aa2a71604b87ffb4936204201d06678341
