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`](https://github.com/rust-lang/rust/blob/017ae1b21f7be6dcdcfc95631e54bde806653a8a/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](https://github.com/zed-industries/zed/blob/0173479d18e2526c1f9c8b25ac94ec66b992a2b2/crates/project/src/lsp_store.rs#L3578)
-
[worktree.rs#L4338](https://github.com/zed-industries/zed/blob/0173479d18e2526c1f9c8b25ac94ec66b992a2b2/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

Cargo.lock

@@ -3752,6 +3752,12 @@ dependencies = [
  "phf",
 ]
 
+[[package]]
+name = "dunce"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "92773504d58c093f6de2459af4af33faa518c13451eb8f2b5698ed3d36e7c813"
+
 [[package]]
 name = "dwrote"
 version = "0.11.2"
@@ -13689,6 +13695,7 @@ dependencies = [
  "async-fs 1.6.0",
  "collections",
  "dirs 4.0.0",
+ "dunce",
  "futures 0.3.31",
  "futures-lite 1.13.0",
  "git2",