Test explorer implementation (src/goTest)

Mapping tests

TestItems themselves cannot be used with Maps. For non-primitive (object) keys, Map uses strict equality. Two objects are only strictly equal to each other if they are the exact same object. Because of this, TestItems cannot be used as map keys, as the extension host may provide different objects for the same test. Therefore, if we want to use TestItems as a map key, we must use their ID instead.