GD-220: Add flaky test handling

[MikeSchulze]

Is your feature request related to a problem? Please describe.

A flaky test is a test which could fail or pass for the same configuration. Flaky tests could be harmful for developers because their failures do not always indicate bugs in the code.

Describe the solution you'd like
Add support to handle flaky tests by add new options to the GdUnit settings.

• enable flaky test handling
• retry count
  Mark such tests as flaky and report the failure and success report.

Describe alternatives you've considered
Without automated retry of the failed test, we need to manually retry the entire test environment.

Additional context

This test are flaky

func test_2s():
	var timer_start := Time.get_ticks_msec()
	await await_millis(2000)
	# subtract an offset of 100ms because the time is not accurate
	assert_int(Time.get_ticks_msec()-timer_start).is_between(2*SECOND-100, 2*SECOND+100)

or