Better absolute path handling (#19727)

Closes #19866

This PR supersedes #19228, as #19228 encountered too many merge
conflicts.

After some exploration, I found that for paths with the `\\?\` prefix,
we can safely remove it and consistently use the clean paths in all
cases. Previously, in #19228, I thought we would still need the `\\?\`
prefix for IO operations to handle long paths better. However, this
turns out to be unnecessary because Rust automatically manages this for
us when calling IO-related APIs. For details, refer to Rust's internal
function
[`get_long_path`](017ae1b21f/library/std/src/sys/path/windows.rs (L225-L233)).

Therefore, we can always store and use paths without the `\\?\` prefix.

This PR introduces a `SanitizedPath` structure, which represents a path
stripped of the `\\?\` prefix. To prevent untrimmed paths from being
mistakenly passed into `Worktree`, the type of `Worktree`’s `abs_path`
member variable has been changed to `SanitizedPath`.

Additionally, this PR reverts the changes of #15856 and #18726. After
testing, it appears that the issues those PRs addressed can be resolved
by this PR.

### Existing Issue
To keep the scope of modifications manageable, `Worktree::abs_path` has
retained its current signature as `fn abs_path(&self) -> Arc<Path>`,
rather than returning a `SanitizedPath`. Updating the method to return
`SanitizedPath`—which may better resolve path inconsistencies—would
likely introduce extensive changes similar to those in #19228.

Currently, the limitation is as follows:

```rust
let abs_path: &Arc<Path> = snapshot.abs_path();
let some_non_trimmed_path = Path::new("\\\\?\\C:\\Users\\user\\Desktop\\project"); 
// The caller performs some actions here:
some_non_trimmed_path.strip_prefix(abs_path);  // This fails
some_non_trimmed_path.starts_with(abs_path);   // This fails too
```

The final two lines will fail because `snapshot.abs_path()` returns a
clean path without the `\\?\` prefix. I have identified two relevant
instances that may face this issue:
-
[lsp_store.rs#L3578](0173479d18/crates/project/src/lsp_store.rs (L3578))
-
[worktree.rs#L4338](0173479d18/crates/worktree/src/worktree.rs (L4338))

Switching `Worktree::abs_path` to return `SanitizedPath` would resolve
these issues but would also lead to many code changes.

Any suggestions or feedback on this approach are very welcome.

cc @SomeoneToIgnore 

Release Notes:

- N/A

crates/fs/src/fs.rs

@@ -452,18 +452,16 @@ impl Fs for RealFs {
 
     #[cfg(target_os = "windows")]
     async fn trash_file(&self, path: &Path, _options: RemoveOptions) -> Result<()> {
+        use util::paths::SanitizedPath;
         use windows::{
             core::HSTRING,
             Storage::{StorageDeleteOption, StorageFile},
         };
         // todo(windows)
         // When new version of `windows-rs` release, make this operation `async`
-        let path = path.canonicalize()?.to_string_lossy().to_string();
-        let path_str = path.trim_start_matches("\\\\?\\");
-        if path_str.is_empty() {
-            anyhow::bail!("File path is empty!");
-        }
-        let file = StorageFile::GetFileFromPathAsync(&HSTRING::from(path_str))?.get()?;
+        let path = SanitizedPath::from(path.canonicalize()?);
+        let path_string = path.to_string();
+        let file = StorageFile::GetFileFromPathAsync(&HSTRING::from(path_string))?.get()?;
         file.DeleteAsync(StorageDeleteOption::Default)?.get()?;
         Ok(())
     }
@@ -480,19 +478,17 @@ impl Fs for RealFs {
 
     #[cfg(target_os = "windows")]
     async fn trash_dir(&self, path: &Path, _options: RemoveOptions) -> Result<()> {
+        use util::paths::SanitizedPath;
         use windows::{
             core::HSTRING,
             Storage::{StorageDeleteOption, StorageFolder},
         };
 
-        let path = path.canonicalize()?.to_string_lossy().to_string();
-        let path_str = path.trim_start_matches("\\\\?\\");
-        if path_str.is_empty() {
-            anyhow::bail!("Folder path is empty!");
-        }
         // todo(windows)
         // When new version of `windows-rs` release, make this operation `async`
-        let folder = StorageFolder::GetFolderFromPathAsync(&HSTRING::from(path_str))?.get()?;
+        let path = SanitizedPath::from(path.canonicalize()?);
+        let path_string = path.to_string();
+        let folder = StorageFolder::GetFolderFromPathAsync(&HSTRING::from(path_string))?.get()?;
         folder.DeleteAsync(StorageDeleteOption::Default)?.get()?;
         Ok(())
     }