Select all matches

[SomeoneToIgnore]

Closes #6208

The PR

• changes keybindings for Editor && mode == auto_height context: before, alt-enter and alt-shift-enter added new lines in such editors, including the one from buffer search.

New bindings are the same as in Editor && mode == full context.

• adds search::SelectAllMatches action and binds it to Alt + Enter by default, to select all matches of a buffer search

The behavior mimics VSCode: we do not move the screen even if all selections are out of the visible range (Cmd+G will navigate there) and allow reselecting the results from both pane and search field, as long as the search is not dismissed.

Release Notes:

• Added search::SelectAllMatches (Alt + Enter default) action to place carets and select all buffer search results (#1749).

[iamnbutler]

This is awesome! Could we add a UI button to search either in this PR or a follow up PR?

[SomeoneToIgnore]

Sure thing!

For now, I did not add any since VSCode did not have that, but no strong opinions.
I am still trying to fix another thing related to the feature: our match counter relies on selections, so it is always n/n items when user presses alt + enter in Zed — while VSCode remembers previous match number and cmd + g shortcuts work better.