Execute remote actions on another extension

[dbwiddis]

Companion PR: #6734 must be merged first

Description

Allows one extension to execute an action on another extension.

See the Hello World RestRemoteHelloAction for sample implementation.

Other work done to support:

• Put a setter on Extension interface to get a copy of extensions runner since injection is flaky.
• Created SDKTransportService class to avoid having to pass around so many params. Lots of things can be moved from ExtensionsRunner there later, just did the action module ones in this PR and left some TODOs where other opportunities exist

Issues Resolved

Fixes #525

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[dbwiddis]

Gradle check is failing based on companion PR classes. No idea why DCO check is failing, git log shows they're all signed. (git rebase --signoff HEAD~9 for the win!)

[owaiskazi19]

Great work on Dynamic Actions @dbwiddis 🙌! Didn't get a chance to review the tests

[dbwiddis]

@owaiskazi19 @saratvemulapalli addressed all your comments.

And as-of now it still works:

curl -X GET http://localhost:9200/_extensions/_hw/hello/test
Received greeting from remote extension: Hello, test%  

[dbwiddis]

Gradle check failing due to companion PR. Only thing left is to update the sequence diagram which I'm working on.

[owaiskazi19]

LGTM! Thanks for incorporating all the suggestions!

[joshpalis]

Looks good to me, thanks @dbwiddis for this.

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (main@467200d). Click here to learn what that means.
The diff coverage is 42.27%.

📣 This organization is not using Codecov’s GitHub App Integration. We recommend you install it so Codecov can continue to function properly for your repositories. Learn more

@@           Coverage Diff           @@
##             main     #588   +/-   ##
=======================================
  Coverage        ?   63.97%           
  Complexity      ?      244           
=======================================
  Files           ?       49           
  Lines           ?     1088           
  Branches        ?       35           
=======================================
  Hits            ?      696           
  Misses          ?      381           
  Partials        ?       11           

Impacted Files	Coverage Δ
src/main/java/org/opensearch/sdk/Extension.java	100.00% <ø> (ø)
...h/sdk/handlers/ExtensionActionResponseHandler.java	0.00% <0.00%> (ø)
...ch/sdk/handlers/ExtensionActionRequestHandler.java	7.27% <7.27%> (ø)
.../sample/helloworld/rest/RestRemoteHelloAction.java	25.00% <25.00%> (ø)
...rch/sdk/action/RemoteExtensionTransportAction.java	37.50% <37.50%> (ø)
...n/java/org/opensearch/sdk/SDKTransportService.java	47.61% <47.61%> (ø)
...earch/sdk/action/RemoteExtensionActionRequest.java	71.79% <71.79%> (ø)
...main/java/org/opensearch/sdk/ExtensionsRunner.java	76.96% <78.57%> (ø)
...rc/main/java/org/opensearch/sdk/BaseExtension.java	86.66% <100.00%> (ø)
src/main/java/org/opensearch/sdk/SDKClient.java	92.00% <100.00%> (ø)
... and 4 more

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.