Adjust interception of requests for specific shard IDs

[gwbrown]

Some index requests target shard IDs specifically, which may not match the indices that the request targets as given by IndicesRequest, which requires a different interception strategy in order to make sure those requests are handled correctly in all cases.

This PR adds and interface allowing requests to report the shard IDs they target as well as the index names, and adjusts the interception of those requests as appropriate to handle those shard IDs in the cases where they are relevant.

[elasticsearchmachine]

Pinging @elastic/es-security (Team:Security)

[elasticsearchmachine]

Hi @gwbrown, I've created a changelog YAML for you.

[gwbrown]

@jakelandis I believe I've addressed the concerns we discussed, could you give me a review?

[gwbrown]

@jakelandis I yes-and'd your idea into "create a writeable that streams the equivalent to a get request"; I think that makes it a bit more maintainable while still letting us remove the test-only production code. I've also expanded the test coverage to cover x-pack, which had a couple implications I Slack'd you about.

[elasticsearchmachine]

💔 Backport failed

Status	Branch	Result
❌	8.13	Commit could not be cherrypicked due to conflicts

You can use sqren/backport to manually backport by running backport --upstream elastic/elasticsearch --pr 101656