Revert "Disable Fontations FontConfig indexing and disregard old caches"

This reverts commit 206882f864fa01256761a755a89054ac61ac3848.

Re-enable Fontations indexing. Indexing issues have been addressed by a
fix in FontConfig. For fonts without family name a name is generated
from the filename. Fonts with incorrect CFF tables are reject, same as
in FreeType indexing.

From 206882f864fa0:

> Note: When reverting this, we need to make sure that if FontConfig cache
> version has not been changed since this was broken, the code then also
> needs to be able to handle cache entries that may have been incorrectly
> added, for example for the HEJI2Text.otf font, see bug.

The FontConfig cache version has been increased to 11 in the previous
FontConfig roll [1], so we no longer need a suffix for our cache files.

[1] https://crrev.com/c/6956169

Enabled-by-default-reason: killswitch
Bug: 442747781
Change-Id: If8e92ad7498cf376c024f871e8778db9d064621e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6954652
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1516516}