Use valid names for custom components / properties

[angatha]

This issue arises from #417. See that PR for more context.

@jacadzaca mentioned at #374 wired test cases. Those where refactored in #417 but the quirk remained in place. At this place and maybe at other locations, there are custom components without the "X-" prefix, so they should be IANA registered names. Since this is not the case, I suggest changing them to x-names since then the test case parses valid ics.

• Update test cases touched in refactor test_issue_178 #417.
• Search for other tests with custom components that may do the same thing.