Ninja and GN are upgraded to the version specified in V8's `DEPS` file
as of V8 11.0.226.2.
As part of this upgrade, native binaries for linux-arm64 and mac-arm64
were added to the repository, and some directories were renamed to make
the overall naming scheme more consistent.
After the upgrade some Deno tests started crashing somewhere deep inside
V8, and the cause of these crashes is unclear.
This reverts the following commits:
* 12334ffe Upgrade gn to 6f13aaac; make BUILD.gn compatible with it (#443)
* f53f10d4 Upgrade V8 to 8.7.25 (#443)
