`DiagROM`-based tests

[Vladyslav Nikonov]

Implement integration tests using functionality available in DiagROM test ROM.

Required testing framework functionality was already implemented (at least partially) in rustzx-test crate

• Memory test 48K
• Memory test 128K + Banked memory test (separate DiagROM menu)
• ULA analysis test
• 50Hz NMI interrupt test
• 128K Videobuffer test
• 128K Contention test