Detect and possibly use user-installed gopls / zls language servers (#8188)

After a lot of back-and-forth, this is a small attempt to implement
solutions (1) and (3) in
https://github.com/zed-industries/zed/issues/7902. The goal is to have a
minimal change that helps users get started with Zed, until we have
extensions ready.

Release Notes:

- Added detection of user-installed `gopls` to Go language server
adapter. If a user has `gopls` in `$PATH` when opening a worktree, it
will be used.
- Added detection of user-installed `zls` to Zig language server
adapter. If a user has `zls` in `$PATH` when opening a worktree, it will
be used.

Example:

I don't have `go` installed globally, but I do have `gopls`:

```
~ $ which go
go not found
~ $ which gopls
/Users/thorstenball/code/go/bin/gopls
```

But I do have `go` in a project's directory:

```
~/tmp/go-testing φ which go
/Users/thorstenball/.local/share/mise/installs/go/1.21.5/go/bin/go
~/tmp/go-testing φ which gopls
/Users/thorstenball/code/go/bin/gopls
```

With current Zed when I run `zed ~/tmp/go-testing`, I'd get the dreaded
error:

![screenshot-2024-02-23-11 14
08@2x](https://github.com/zed-industries/zed/assets/1185253/822ea59b-c63e-4102-a50e-75501cc4e0e3)

But with the changes in this PR, it works:

```
[2024-02-23T11:14:42+01:00 INFO  language::language_registry] starting language server "gopls", path: "/Users/thorstenball/tmp/go-testing", id: 1
[2024-02-23T11:14:42+01:00 INFO  language::language_registry] found user-installed language server for Go. path: "/Users/thorstenball/code/go/bin/gopls", arguments: ["-mode=stdio"]
[2024-02-23T11:14:42+01:00 INFO  lsp] starting language server. binary path: "/Users/thorstenball/code/go/bin/gopls", working directory: "/Users/thorstenball/tmp/go-testing", args: ["-mode=stdio"]
```

---------

Co-authored-by: Antonio <antonio@zed.dev>

Cargo.lock

@@ -1351,7 +1351,7 @@ dependencies = [
  "rustc-hash",
  "shlex",
  "syn 2.0.48",
- "which",
+ "which 4.4.2",
 ]
 
 [[package]]
@@ -4348,11 +4348,11 @@ dependencies = [
 
 [[package]]
 name = "home"
-version = "0.5.5"
+version = "0.5.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5444c27eef6923071f7ebcc33e3444508466a76f7a2b93da00ed6e19f30c1ddb"
+checksum = "e3d1354bf6b7235cb4a0576c2619fd4ed18183f689b12b006a0ee7329eeff9a5"
 dependencies = [
- "windows-sys 0.48.0",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
@@ -6942,6 +6942,7 @@ dependencies = [
  "toml 0.8.10",
  "unindent",
  "util",
+ "which 6.0.0",
 ]
 
 [[package]]
@@ -7051,7 +7052,7 @@ dependencies = [
  "prost-types 0.9.0",
  "regex",
  "tempfile",
- "which",
+ "which 4.4.2",
 ]
 
 [[package]]
@@ -11425,6 +11426,19 @@ dependencies = [
  "rustix 0.38.30",
 ]
 
+[[package]]
+name = "which"
+version = "6.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fa5e0c10bf77f44aac573e498d1a82d5fbd5e91f6fc0a99e7be4b38e85e101c"
+dependencies = [
+ "either",
+ "home",
+ "once_cell",
+ "rustix 0.38.30",
+ "windows-sys 0.52.0",
+]
+
 [[package]]
 name = "whoami"
 version = "1.4.1"