feat: enhance Go tree-sitter parser with advanced language structures

This enhancement significantly expands the Go parser's capabilities to recognize and extract a comprehensive set of language constructs:

- Added support for struct and interface definitions with proper type identification
- Implemented parsing for constant declarations (both single and in blocks)
- Added support for variable declarations (both single and in blocks)
- Added recognition of type aliases with proper distinction from regular types
- Implemented special handling for init functions
- Added support for anonymous functions, including nested function literals
- Improved documentation and organization of query patterns

These enhancements enable more accurate code navigation, better symbol extraction, and improved code intelligence for Go codebases.

Signed-off-by: Eric Wheeler <[email protected]>

Author: Eric Wheeler