Simplify finding metrics in Summarize (#46887)

* Use global search for aggregation picker

* Add names to aggregation picker items so they can be searched

* Render info icon metric descriptions

* Add unit tests for global aggregation picker search

* Add test for searching metrics

* Add a test for metrics descriptions

* Sort metrics

* Fix e2e test

* Use Flex from metabase/ui

* Handle markdown in metric description

* Add test for sorted metrics

* Update Markdown styling in metric description

* Fix clojure formatting

* Test for markdown in the Metric description

* Fix lint

* Fix test for markdown

* Use simpler equality test

* Fix overflow in test