Runtime exclude/include

[kevinresol]

Code like https://github.com/haxetink/tink_sql/blob/de2c6db5bb7e0b6f78ae358e8f6dba550082293c/tests/SubQueryTest.hx#L66-L80 could be rewritten as:

@:condition(this.driver.type == MySql)
public function anyFunc():Assertions {...}