fs: Replace a bunch of uses of smol::fs with manual impls (#40172)

smol::fs uses a separate threadpool, which is a bit yuck.

This PR also added a benchmark you can use to run a full worktree scan
(initial one, that is) for arbitrary worktree.. and refactored worktree
scanner to use async locks, as otherwise tests were deadlocking. :)
I've benchmarked it against Zed, Linux and Chromium and saw a ~60% drop
in initial worktree scan times across the board.
Release Notes:

- Significantly (3.3x speedup over the old implementation) improved
speed of Zed's worktree scanner, that's responsible for synchronizing
the state of your project with the state of files on hard drive.

---------

Co-authored-by: Smit Barmase <heysmitbarmase@gmail.com>

Cargo.lock

@@ -1166,7 +1166,7 @@ version = "2.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "09f7e37c0ed80b2a977691c47dae8625cfb21e205827106c64f7c588766b2e50"
 dependencies = [
- "async-lock",
+ "async-lock 3.4.1",
  "blocking",
  "futures-lite 2.6.0",
 ]
@@ -1180,7 +1180,7 @@ dependencies = [
  "async-channel 2.3.1",
  "async-executor",
  "async-io",
- "async-lock",
+ "async-lock 3.4.1",
  "blocking",
  "futures-lite 2.6.0",
  "once_cell",
@@ -1192,7 +1192,7 @@ version = "2.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "19634d6336019ef220f09fd31168ce5c184b295cbf80345437cc36094ef223ca"
 dependencies = [
- "async-lock",
+ "async-lock 3.4.1",
  "cfg-if",
  "concurrent-queue",
  "futures-io",
@@ -1204,6 +1204,15 @@ dependencies = [
  "windows-sys 0.60.2",
 ]
 
+[[package]]
+name = "async-lock"
+version = "2.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "287272293e9d8c41773cec55e365490fe034813a2f172f502d6ddcf75b2f582b"
+dependencies = [
+ "event-listener 2.5.3",
+]
+
 [[package]]
 name = "async-lock"
 version = "3.4.1"
@@ -1243,7 +1252,7 @@ checksum = "63255f1dc2381611000436537bbedfe83183faa303a5a0edaf191edef06526bb"
 dependencies = [
  "async-channel 2.3.1",
  "async-io",
- "async-lock",
+ "async-lock 3.4.1",
  "async-signal",
  "async-task",
  "blocking",
@@ -1272,7 +1281,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "637e00349800c0bdf8bfc21ebbc0b6524abea702b0da4168ac00d070d0c0b9f3"
 dependencies = [
  "async-io",
- "async-lock",
+ "async-lock 3.4.1",
  "atomic-waker",
  "cfg-if",
  "futures-core",
@@ -1293,7 +1302,7 @@ dependencies = [
  "async-channel 1.9.0",
  "async-global-executor",
  "async-io",
- "async-lock",
+ "async-lock 3.4.1",
  "async-process",
  "crossbeam-utils",
  "futures-channel",
@@ -6528,6 +6537,15 @@ dependencies = [
  "windows-sys 0.59.0",
 ]
 
+[[package]]
+name = "fs_benchmarks"
+version = "0.1.0"
+dependencies = [
+ "fs",
+ "gpui",
+ "workspace-hack",
+]
+
 [[package]]
 name = "fs_extra"
 version = "1.3.0"
@@ -11034,7 +11052,7 @@ dependencies = [
  "ashpd 0.12.0",
  "async-fs",
  "async-io",
- "async-lock",
+ "async-lock 3.4.1",
  "blocking",
  "cbc",
  "cipher",
@@ -15735,7 +15753,7 @@ dependencies = [
  "async-executor",
  "async-fs",
  "async-io",
- "async-lock",
+ "async-lock 3.4.1",
  "async-net",
  "async-process",
  "blocking",
@@ -20849,6 +20867,7 @@ name = "worktree"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "async-lock 2.8.0",
  "clock",
  "collections",
  "fs",
@@ -20879,6 +20898,17 @@ dependencies = [
  "zlog",
 ]
 
+[[package]]
+name = "worktree_benchmarks"
+version = "0.1.0"
+dependencies = [
+ "fs",
+ "gpui",
+ "settings",
+ "workspace-hack",
+ "worktree",
+]
+
 [[package]]
 name = "write16"
 version = "1.0.0"
@@ -21150,7 +21180,7 @@ dependencies = [
  "async-broadcast",
  "async-executor",
  "async-io",
- "async-lock",
+ "async-lock 3.4.1",
  "async-process",
  "async-recursion",
  "async-task",