Short variable declaration in a 'for' loop should be outside the for_clause

[bhaible]

A program that tracks the meaning of variables can usually work like this:

• Recursive traversal through the TSNode tree.
• When encountering a var_declaration, const_declaration, or short_var_declaration, take note of the variables in these declarations, which have a scope that lasts until the end of the current recursion level.

This simple algorithm works fine

• for function definitions,
• for blocks,
• for the short_var_declaration in if and switch statements (cf. https://go.dev/ref/spec#If_statements and https://go.dev/ref/spec#Switch_statements).

But for the short_var_declaration in a for statement (cf. https://go.dev/ref/spec#For_statements), it does not work, because what tree-sitter returns has the structure

(for_statement (for_clause initializer: (short_var_declaration ...) ...) ...)

Here the program has to special-case for_statement and pull out the initializer field from the for_clause. This is cumbersome. It would be simpler if tree-sitter returned a structure like this:

(for_statement initializer: (short_var_declaration ...) (for_clause ...) ...)

How to reproduce:
Process this input file:

package main

import "fmt"

var z [5]string

func main() {
    for z := 1; z < 5; z++ {
        fmt.Printf("%v\n", z)
    }
}

The syntax tree that tree-sitter produces is:

(source_file (package_clause (package_identifier)) (import_declaration (import_spec path: (interpreted_string_literal (interpreted_string_literal_content)))) (var_declaration (var_spec name: (identifier) type: (array_type length: (int_literal) element: (type_identifier)))) (function_declaration name: (identifier) parameters: (parameter_list) body: (block (for_statement (for_clause initializer: (short_var_declaration left: (expression_list (identifier)) right: (expression_list (int_literal))) condition: (binary_expression left: (identifier) right: (int_literal)) update: (inc_statement (identifier))) body: (block (expression_statement (call_expression function: (selector_expression operand: (identifier) field: (field_identifier)) arguments: (argument_list (interpreted_string_literal (interpreted_string_literal_content) (escape_sequence)) (identifier)))))))))