Improve Go syntax highlighting (#25327)

Release Notes:

  - Improved Go syntax highlighting.

| Zed 0.174.6 | With this PR |
| --- | --- |
|
![Image](https://github.com/user-attachments/assets/7f6113cb-0517-4ea7-a979-902a2373314e)
|
![Image](https://github.com/user-attachments/assets/0cf07ebc-c5bd-4269-af7a-49496305d265)
|

- `package_identifier`: `namespace`, language-agnostic scope for
modules, packages, namespaces
- `method_elem`: `function.method`
- `;` ,`.` ,`,` ,`:`: `punctuation.delimiter`

```go
package my_package
import (
  pkg "fmt"
)
type A interface {
  method_elem(foo int, bar float64) int
}
func main() {
  identifier := true
  const constant int = 3
  for i := 0; i <= 3; i++ {
    pkg.Println(identifier)
  }
}
```

---------

Co-authored-by: Marshall Bowers <git@maxdeviant.com>

crates/languages/src/go/highlights.scm

@@ -2,6 +2,7 @@
 
 (type_identifier) @type
 (field_identifier) @variable.member
+(package_identifier) @namespace
 
 (keyed_element
   .
@@ -20,6 +21,15 @@
 
 (method_declaration
   name: (field_identifier) @function.method)
+(method_elem
+  name: (field_identifier) @function.method)
+
+[
+  ";"
+  "."
+  ","
+  ":"
+] @punctuation.delimiter
 
 [
   "("