Sort completions by relevance for strong matches (#20145)

Further enhancement:
On exploring VSCode's sorting logic, there are two major distinctions:
* A config option exists to adjust sort priority of snippets. They can
be placed inline (default), top or at bottom of completitions.
* The sorting order sorts by (in order): sort_text (lower case),
sort_text, kind

ref:
https://github.com/microsoft/vscode/blob/6f2d4781e857a550b7e9b05d40b969c840e264db/src/vs/editor/contrib/suggest/browser/suggest.ts#L338-L383

Closes #19786

Release Notes:

- Improved sort order in completions to show relevant matches first
([#19786](https://github.com/zed-industries/zed/issues/19786))