fix(ngMessageFormat): minified symbol and nested required expression

Add an E2E test that works against the minified module to test that the
minified build works correctly.

Fix a bug where mustHaveExpression was passed through to submessages
unchanged. Use of the messageFormat syntax automatically means that you
are using an expression.  Therefore, submessages should not be required
to also have messages.

Closes #11414
Closes #11592