util: add fuchsia helpers

Implementation moved to util from the non-upstreamable location.

Also implement initialize_tracing(). While this isn't really useful for
Lavapipe, it doesn't hurt to have it, and since we use magma logging
for Lavapipe it's simple to just have them both.

Bug:460783239
Change-Id: I47aa5d1a4d4dc3f63b3907b59a6b048f74bff8e4
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/mesa/+/1438476
Reviewed-by: David Gilhooley <dgilhooley@google.com>