…38726)

Commit Message:
- Add a `keep_matching` field to OnMatch to mark Matchers that should be
recorded when matched but should not be the final matched + enforced
action.
- Implement support for `keep_matching` using MatcherTree re-entry.
- Re-entry is implemented in PR #38564 as well for a separate review if
this PR gets closed.
- ListMatcher was chosen as the simplest example usecase /
proof-of-concept for re-entry, but implementation in other MatcherTree
children will follow in separate PRs (namely prefix_map_matcher).
- Centralize recursion handling & re-entry logic into
`evaluateMatch(...)`, leaving each MatchTree child class to implement
the simplest possible `match(...)` logic (find a match and return it +
optionally a reentrant).
- Previously recursion handling was inconsistent across the MatchTree
children, and this saves each child from having to re-implement
recursion, `keep_handling` processing, etc.
- TrieMatcher also required a reentrant implementation as part of moving
recursion logic out of its `match(...)` logic.


Additional Description:
- The final goal is to implement preview / darklaunch Matchers whose
actions are logged or added to metadata, but not enforced.
- An initial implementation of preview matched actions just using
re-entry was drafted for the rate_limit_quota filter in PR #38576,
prompting the request to instead add this `keep_matching` feature to the
Matcher API for re-usability.
- This change will also depend on a duplicate, matcher proto change in
[github.com/cnf/xds](cncf/xds#117).

Risk Level: moderate - includes changes to widely-used libraries
Testing: Unit + Integration testing, loadtesting WIP
Docs Changes:
Release Notes:
Platform Specific Features:
~[Optional Runtime guard:]~
~[Optional Fixes #Issue]~
~[Optional Fixes commit #PR or SHA]~
~[Optional Deprecated:]~
[API
Considerations](https://github.com/envoyproxy/envoy/blob/main/api/review_checklist.md):
The new `keep_matching` field is not marked as WIP as its implementation
should be tested for any breaking changes.

---------

Signed-off-by: Brian Surber <[email protected]>
Signed-off-by: Raven Black <[email protected]>
Co-authored-by: Raven Black <[email protected]>