…tions

Add simple search proxy

…de API (elastic#234571)

**Partially resolves: elastic#140369**

## Summary

This is another PR from of a series of PRs I am planning to create to
cover the requirements in the elastic#140369 ticket.

The requirement covered in this ticket is req. #6: "Events for
performing update (EBT backend)" and req. #7 "Missing base versions".

I am adding sending telemetry events in handling of rule update request.
Each rule updated will send its own event with information about:
- ruleId
- ruleName
- if missing base version
- final result of the update
- updated fields (with breakdown per conflict type). 

I tried to make the changes as little invasive as possible, and decided
to create a separate file, `update_rule_telemetry.ts`, where the logic
of building the events and sending them is encapsulated.

### Checklist

Check the PR satisfies following conditions. 

Reviewers should verify this PR satisfies this list as well.

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [x] [Flaky Test
Runner](https://ci-stats.kibana.dev/trigger_flaky_test_runner/1) was
used on any tests changed
- [x] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)
- [ ] Review the [backport
guidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)
and apply applicable `backport:*` labels.