gpui: Implement From<String> for ElementId (#44447)

Release Notes:

- N/A

## Before

```rs
div()
    .id(SharedString::from(format!("process-entry-{ix}-command")))
```

## After

```rs
div()
    .id(format!("process-entry-{ix}-command"))
```

crates/git_ui/src/branch_picker.rs

@@ -911,7 +911,7 @@ impl PickerDelegate for BranchListDelegate {
         });
 
         Some(
-            ListItem::new(SharedString::from(format!("vcs-menu-{ix}")))
+            ListItem::new(format!("vcs-menu-{ix}"))
                 .inset(true)
                 .spacing(ListItemSpacing::Sparse)
                 .toggle_state(selected)

crates/git_ui/src/picker_prompt.rs

@@ -220,7 +220,7 @@ impl PickerDelegate for PickerPromptDelegate {
         let shortened_option = util::truncate_and_trailoff(&hit.string, self.max_match_length);
 
         Some(
-            ListItem::new(SharedString::from(format!("picker-prompt-menu-{ix}")))
+            ListItem::new(format!("picker-prompt-menu-{ix}"))
                 .inset(true)
                 .spacing(ListItemSpacing::Sparse)
                 .toggle_state(selected)

crates/git_ui/src/stash_picker.rs

@@ -464,7 +464,7 @@ impl PickerDelegate for StashListDelegate {
             );
 
         Some(
-            ListItem::new(SharedString::from(format!("stash-{ix}")))
+            ListItem::new(format!("stash-{ix}"))
                 .inset(true)
                 .spacing(ListItemSpacing::Sparse)
                 .toggle_state(selected)

crates/git_ui/src/worktree_picker.rs

@@ -665,7 +665,7 @@ impl PickerDelegate for WorktreeListDelegate {
         };
 
         Some(
-            ListItem::new(SharedString::from(format!("worktree-menu-{ix}")))
+            ListItem::new(format!("worktree-menu-{ix}"))
                 .inset(true)
                 .spacing(ListItemSpacing::Sparse)
                 .toggle_state(selected)