editor: Move blame popover from hover_tooltip to editor prepaint (#29320)

WIP!

In light of having more control over blame popover from editor.

This fixes: https://github.com/zed-industries/zed/issues/28645,
https://github.com/zed-industries/zed/issues/26304

- [x] Initial rendering
- [x] Handle smart positioning (edge detection, etc)
- [x] Delayed hovering, release, etc
- [x] Test blame message selection
- [x] Fix tagged issues

Release Notes:

- Git inline blame popover now dismisses when the cursor is moved, the
editor is scrolled, or the command palette is opened.

crates/git_ui/src/commit_tooltip.rs

@@ -27,22 +27,18 @@ pub struct CommitDetails {
     pub message: Option<ParsedCommitMessage>,
 }
 
-struct CommitAvatar<'a> {
+pub struct CommitAvatar<'a> {
     commit: &'a CommitDetails,
 }
 
 impl<'a> CommitAvatar<'a> {
-    fn new(details: &'a CommitDetails) -> Self {
+    pub fn new(details: &'a CommitDetails) -> Self {
         Self { commit: details }
     }
 }
 
 impl<'a> CommitAvatar<'a> {
-    fn render(
-        &'a self,
-        window: &mut Window,
-        cx: &mut Context<CommitTooltip>,
-    ) -> Option<impl IntoElement + use<>> {
+    pub fn render(&'a self, window: &mut Window, cx: &mut App) -> Option<impl IntoElement + use<>> {
         let remote = self
             .commit
             .message