extension: Upgrade wasmtime to v21 (#15210)

This PR upgrades the version of `wasmtime` and `wasmtime-wasi` in use to
v21.0.1.

We have to skip v20 because Tree-sitter also skipped it.

Here are the changes that had to be made:

### v19 -> v20

After upgrading the `wasmtime` packages to v20, I also had to run `cargo
update -p mach2` to pull in
[v0.4.2](https://github.com/JohnTitor/mach2/releases/tag/0.4.2) to fix
some compile errors.

There were a few minor API changes in `wasmtime-wasi` from
https://github.com/bytecodealliance/wasmtime/pull/8228 that we needed to
account for.

### v20 -> v21

Since there isn't a Tree-sitter version that depends on `wasmtime@v20`,
we're jumping straight to v21.

The published version of Tree-sitter (v0.22.6) still depends on
`wasmtime@v19`, but there was a commit
(https://github.com/tree-sitter/tree-sitter/commit/7f4a57817d58a2f134fe863674acad6bbf007228)
later that month that upgrades the `wasmtime` dependency to v21.

We're patching Tree-sitter to that commit so we can get the new
`wasmtime` version.

The main change in v21 is that imports generated by `bindgen!` are no
longer automatically trapped
(https://github.com/bytecodealliance/wasmtime/pull/8310), so we need to
add `trappable_imports: true` to our `bindgen!` calls.

Release Notes:

- N/A

Cargo.toml

@@ -304,7 +304,6 @@ bitflags = "2.6.0"
 blade-graphics = { git = "https://github.com/zed-industries/blade", rev = "7e497c534d5d4a30c18d9eb182cf39eaf0aaa25e" }
 blade-macros = { git = "https://github.com/zed-industries/blade", rev = "7e497c534d5d4a30c18d9eb182cf39eaf0aaa25e" }
 blade-util = { git = "https://github.com/zed-industries/blade", rev = "7e497c534d5d4a30c18d9eb182cf39eaf0aaa25e" }
-cap-std = "3.0"
 cargo_toml = "0.20"
 chrono = { version = "0.4", features = ["serde"] }
 clap = { version = "4.4", features = ["derive"] }
@@ -432,14 +431,14 @@ url = "2.2"
 uuid = { version = "1.1.2", features = ["v4", "v5", "serde"] }
 wasmparser = "0.201"
 wasm-encoder = "0.201"
-wasmtime = { version = "19.0.2", default-features = false, features = [
+wasmtime = { version = "21.0.1", default-features = false, features = [
     "async",
     "demangle",
     "runtime",
     "cranelift",
     "component-model",
 ] }
-wasmtime-wasi = "19.0.2"
+wasmtime-wasi = "21.0.1"
 which = "6.0.0"
 wit-component = "0.201"
 sys-locale = "0.3.1"
@@ -483,6 +482,10 @@ features = [
     "Win32_UI_WindowsAndMessaging",
 ]
 
+[patch.crates-io]
+# Patch Tree-sitter for updated wasmtime.
+tree-sitter = { git = "https://github.com/tree-sitter/tree-sitter", rev = "7f4a57817d58a2f134fe863674acad6bbf007228" }
+
 [profile.dev]
 split-debuginfo = "unpacked"
 debug = "limited"