Expiration policy for signal requestIDs in mutable state

Is your feature request related to a problem? Please describe.
Today if workflow is signal directly via the Signal api (not workflow-to-workflow signal), signal requestID will be store in workflow mutable state forever, which will result in an increase in mutable state size, which could lead to performance issue when say there're 30K signal requestIDs.

Describe the solution you'd like

• Simply rely on the existing max signal count limit.
• Give up the existing guarantee we have on signal deduplication and remove those requestIDs before workflow is closed.
  • Expire requestID based on time (still need to enforce the max signal count limit)
  • Expire requestID based on count

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
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Start with the signal API path and the workflow mutable state that stores signal requestIDs. Read how the existing maximum signal count limit is enforced, then compare the proposed time-based, count-based, and workflow-close expiration options. Done requires a decided policy and an agreed way to preserve the maximum signal count limit while addressing unbounded state growth.