Add most used functions to suggestions when they open (#41267)

* Add list of most popular functions and aggregations

* Render 'All functions' link on expression dropdown

* Suggest popular functions when no input is given

* Do not return focus to search bar

* Default to not matching any substring

* Open suggestions when the expression editor opens

* Group expressions by group

* Render group titles in dropdown

* Match the expression suggestions height to the design

* Add tests for popular functions

* Convert tests to it-style

* Only return supported popular functions

* Limit most used functions group to 5 items

* Make the suggestion footer keyboard-accessible

* Make a different group for popular aggregations

* Remove padding on suggestion list

* Resize list

* Add test for popular functions in suggest

* Move showMetabaseLinks into args

* Remove unneeded optional chain

* Clarify popup issue in ACE hack

* Use correct target for links

* Reference correct method in comment

* Split up popular expressions

* Remove Set around popular functions/aggregations

* Do not allow interacting with suggestion header

* Do not use _ prefix for variable

* Add verb in test

* Remove unused async in test

* Test if functions are in document

* Move tests for suggestWithFooter to separate file

* Use correct target in link

* Fix typo in key

* Allow picking suggestion when textbox is empty

* Remove unnecessary cast

* Avoid double scroll bars

* Only show link to all functions when editor is empty

* Split up popular functions between expressions and filters

* Fix type of popular variable

* Use the same heuristic for footer as for popular expressions

* Close suggestions when the editor is not focused

* Add missing open prop in test

* Simplify test

* Add selector for expression editor widget

* Fix e2e tests

Fix e2e tests

* Avoid non-interactive clicks from closing the dropdown

* Use custom expression helpers in broken test

* Fix test

* Remove should exist check for selector