`marl::Scheduler::setWorkerThreadCount()` and `marl::Scheduler::setThreadInitializer()` have been deprecated.
`marl::Scheduler::Config` is the new API.

See https://github.com/google/marl/issues/139 for context.

Bug: b/140546382
Change-Id: Ida768eea98a7ca5d22f55f5055ca288b41b353d0
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/45493Tested-by: Ben Clayton <bclayton@google.com>
Presubmit-Ready: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>