Cleanup clipboard tests
As requested in #21111, I've refactored the original clipboard tests as well as adding my own.  The set of tests have been improved to include testing of:

- failure of tab delimited tables (#21104)
- errors relating to copying and reading space-delimited tables
- copy and pasting tables where the text contains quotes or delimiters

As a result, these tests will fail on the current master branch, but should succeed on the commit in #21111

@WillAyd