Remote Execution: Support instance names in action-cache-service

Background

We should support instance names for the remote-execution/action-cache-service configuration option.

#628 (closed) added instance names for the storage and execution services, but action-cache-service was added in parallel and didn't get the updates for instance names.

Task description

• Add instance-name parameter to action-cache-service which is consistent with the parameter for storage and execution services.

Acceptance Criteria

Test against BuildGrid's Action Cache service using a non-null instance name.

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