go: Add go-generate runnables and tasks (#19987)

I was missing the `go generate` runnable from other editors so I figured
I'd implement one here! Now, comments of the form `//go:generate` can
prompt for the `go generate <package>` task. Meanwhile, I've also added
a global `go generate ./...` task.

~When making the global task, I noticed that the existing `go test
./...` task runs tests in subdirectories of the CWD of the active
editor, whereas I would really expect it to run all tests across my
project. I have changed to use the latter behavior (run relative to
project root) for both `go generate ./...` and `go test ./...`. Please
let me know if the prior behavior was intended, and I can revert.~

Release Notes:

- Added runnable and tasks for `go generate` commands

crates/languages/src/go.rs

@@ -549,6 +549,21 @@ impl ContextProvider for GoContextProvider {
                 tags: vec!["go-main".to_owned()],
                 ..TaskTemplate::default()
             },
+            TaskTemplate {
+                label: format!("go generate {}", GO_PACKAGE_TASK_VARIABLE.template_value()),
+                command: "go".into(),
+                args: vec!["generate".into()],
+                cwd: package_cwd.clone(),
+                tags: vec!["go-generate".to_owned()],
+                ..TaskTemplate::default()
+            },
+            TaskTemplate {
+                label: "go generate ./...".into(),
+                command: "go".into(),
+                args: vec!["generate".into(), "./...".into()],
+                cwd: package_cwd.clone(),
+                ..TaskTemplate::default()
+            },
         ]))
     }
 }

crates/languages/src/go/runnables.scm

@@ -7,6 +7,13 @@
   (#set! tag go-test)
 )
 
+; `go:generate` comments
+(
+    ((comment) @_comment @run
+    (#match? @_comment "^//go:generate"))
+    (#set! tag go-generate)
+)
+
 ; `t.Run`
 (
   (