[infra] Initial version of mesa BUILD.gn rules

First pass at building mesa using meson via GN templates. Specifically
this includes a wrapper for meson based builds, and runs it for mesa
when the tint fuzzer is built. This has successfully built the
software drivers locally, but has not been tested wrt linking/using
these outputs.

I fully expect this will need further adjustments as part of
integrating it into the fuzzer binary.

All of this work is guarded by a build flag and a DEPS flag, so should
not be downloaded or built unless someone intentionally turns it on.

Bug: 475840954

Change-Id: If132898831627cb7a1fdab54dd57de8f59c24e63
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/286395
Reviewed-by: dan sinclair <dsinclair@chromium.org>
Auto-Submit: Ryan Harrison <rharrison@chromium.org>
Commit-Queue: dan sinclair <dsinclair@chromium.org>