Adds proper handling of ExecutorProviders initialization and shutdown

What does this MR do?

Adds a general interface for initializing and shutting-down Executor providers.

Why was this MR needed?

Some of the Executor Providers (like the newly introduced internal autoscaler) may require an initialization of a management layer and a proper shutdown to be done before Runner process exits.

This MR introduced a general mechanism in the ExecutorProvider interface as well as adds implementation for the autoscaler provider.

Please see #29313 (closed) for more details.

What's the best way to test this MR?

What are the relevant issue numbers?

Closes #29313 (closed)