Check for worker indexing capability and redirect to worker indexing pipeline when appropriate

[anandagopal6]

The worker indexing code path should only be selected once the worker indexing capability has been confirmed and the feature flag has been enabled.

At the moment, the code path can be manually switched in ScriptHost.InitializeAsync

Capability and feature flag checks still need to be implemented.

[anandagopal6]

Added feature flag for enabling worker indexing. This feature flag should work in tandem with the indexing capability until the feature flag is removed. For now, the enabled feature flag redirects to the worker indexing pipeline.

[anandagopal6]

Capability service has been added to my local branch. It stores capabilities for each worker runtime in a central structure. Every time a new worker channel sends its capabilities to the host, we update the _workerCapabilities structure in WorkerCapabilities that can later be queried through GetCapabilityValue(runtimeLanguage, capabilityName).

[anandagopal6]

Update: it turns out that worker capabilities are not accessible/exchanged at ScriptHost startup if placeholder mode is not enabled. Because of this, we are now checking the worker config file for the worker indexing ability.

The feature flag has been made and is currently hiding the entire worker-indexing codepath in the host.

To determine whether the worker should index or not, there is a utility function call CanWorkerIndex that will take in a worker config, consult that file, and then also check to see if the feature flag is enabled. If both of these pieces of information are true/enabled, then the util function returns true.

[fabiocav]

This has been merged into the feature branch. Closing as done.