GetActions: Add support to dynamically register actions

[saratvemulapalli]

• Dynamically register transport actions in ActionModule

Transport Actions in extensions are registered with ExtensionsManager via Proxy Actions. But eventually we need make ActionModule dynamic to help register/de-register with OpenSearch

[minalsha]

This is also needed in future for hot-swap, right?

[owaiskazi19]

This is also needed in future for hot-swap, right?

Yes

[dbwiddis]

Right now transport actions are registered in a map which is:

• final
• unmodifiable

Sarat's draft PR linked above removed the unmodifiable bit for that map. However, I'm going to approach this in #525 by just adding a second dynamic map, and integrate the transportAction(action) method to check both maps. Other than that the implementation will be similar to the draft PR.