fix(sub-tests): supports subtests with an identifier

[florentcigolotti]

The :lua require('dap-go').debug_test() function is not working for all sub tests. That is because right now, the TreeSitter subtests_query is written with just a func_literal in the arguments's call_expression.
It is often the case to use it with a literal, see example below:

package test

import (
	"testing"
)

func TestWithSubTests(t *testing.T) {
	t.Run("subtest with function literal (is already working)", func(t *testing.T) {})
	myFunc := func(t *testing.T) {}
	t.Run("subtest with identifier", myFunc)
}

Previously, running :lua require('dap-go').debug_test() with the cursor on the line with t.Run("subtest with identifier", myFunc) was running the parent test TestWithSubTests which is running all subtests.
WIth this pull request, now running the debug_test() is going to run the test subtest with identifier only.

[leoluz]

Thank you for this improvement. I'll give this a local test and merge if it works as expected.

[florentcigolotti]

Would first say thank you for cooking this plugin 👍 Works great and I am very happy to share back to the community.