Test for test_blargg_instr_timing.

This allows background to take precedence over objects.
This completes the CGB ACID 2 test compliance.

There may be a performance impact involved.

Running under a single call.
This required increasing variable size from u8 to u16.

Created infrastructure that allows the usage of the serial device to capture the result of the tests.
Then the test is executed agains a pre-defined number of cycles and the result is compared against expectation.

Adds this CPU speed print support to the web debug panel.

This makes it possible to select CBG or DMG mode taking into consideration the CGB flag in the ROM file.