proposal: testing: per-test setup and teardown support

[PapaCharlie]

This is a follow up issue for #27927 (comment), which discussed having an alternative mechanism to run tests from within TestMain. The proposal was the following:

func TestMain(m *testing.M) {
	setupAll()
	code := m.RunEach(func(t *testing.T) {
		setup(t)
		t.Run()
		teardown(t)
	})
	teardownAll()
	os.Exit(code)
}

Basically, testing.M should provide a way to iterate through the tests and allow code to be executed before and after each.

Originally posted by @mgwidmann in #27927 (comment)

[gabyhelp]

Related Issues and Documentation

• proposal: testing: add support for individual test function execution - expose testing.M.Tests #53701 (closed)
• proposal: testing: per-test setup and teardown support #27927 (closed)
• testing: add M.Cleanup #42161 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[seankhliao]

Duplicate of #53701