Remove ppapi/generators

This is a reland of https://crrev.com/c/6729535

It was reverted in https://crrev.com/c/6729435 because there was
a dependency on these files from the extensions API schema compiler. The
relevant files have now been copied over to //tools/json_schema_compiler
in https://crrev.com/c/6730496, so this change can reland.

Bug: 40511454
Change-Id: I63e74ae58fc43108b67436df281f33bb5228fa67
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6757842
Reviewed-by: Tim <tjudkins@chromium.org>
Auto-Submit: Derek Schuff <dschuff@chromium.org>
Commit-Queue: Derek Schuff <dschuff@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1487220}
NOKEYCHECK=True
GitOrigin-RevId: 47940ab8bb9439cf20299d54a7f70fe584d9c73b