Update rtc3test to v4

The vendored `rtc3test` is based on v3 that was manually modified to show each page as a seperate rom. This split would need to be done again but for v4.

v4 changelog:
> Some optimized code, and much tighter tolerances for the timing tests. This ensures that implementations that, for instance, round tick times to frames aren't accidentally shown as passing the tests.

Source: https://github.com/aaaaaa123456789/rtc3test

Start with the vendored rtc3test and compare its current v3-based structure with the v4 source and changelog. Reproduce the existing manual split so each v4 page is a separate ROM, then verify that the updated timing tests are included and usable.

Written by the indexing model from the issue text.