fix: Diagnose everything in nested items, not just def diagnostics
Turns out we only calculated def diagnostics for these before (was wondering why I wasn't getting any type mismatches)
internal: Migrate assists to the structured snippet API, part 4
Continuing from #15260
Migrates the following assists:
- `add_turbo_fish`
- `add_type_ascription`
- `destructure_tuple_binding`
- `destructure_tuple_binding_in_subpattern`
I did this a while ago, but forgot to make a PR for the changes until now. 😅
minor: Allow multiple snippet edits in a `TextDocumentEdit`
Explicitly[^1] allow a single `TextDocumentEdit` to have multiple `SnippetTextEdit`s. This allows things like renaming extracted variables and functions without having to go through a separate rename step. For an example of what this looks like, see the video in [this comment](https://github.com/microsoft/vscode/issues/145374#issuecomment-1177341711).
The behavior described here lines up with [what VSCode does](bdc113ffe1/src/vscode-dts/vscode.d.ts (L3728-L3731)), and presumably what the eventual LSP behavior will be.
[^1]: This was technically the case before #15269, a single `TextDocumentEdit` always had multiple edits which were `InsertTextFormat.Snippet` as all of the edits were marked as being snippets, even if there weren't any tab stops or placeholders.
minor: Make "Expand macro" command title more explicit
Closes [#15856](https://github.com/rust-lang/rust-analyzer/issues/15856).
I opted for "caret", since it's the better term (cursor is the mouse), but I'm not sure how popular it is these days.
Due to the way the current tree mutation api works, we need to collect
changes before we can apply them to the real syntax tree, and also can only
switch to a file once.
`destructure_tuple_binding_in_sub_pattern` also gets migrated even
though can't be used.
