Add Earlgrey OpenTitan regression flow

[jwnrt]

Adds a CI workflow which runs a pull request's QEMU against the latest OpenTitan earlgrey_1.0.0 tests. This takes ~30 minutes at the moment.

There is a list of tests in the script which it compares against. The workflow fails if:

• Expected tests fail (a regression has happened)
• Unexpected tests pass (the list needs updating)

It runs on pull requests or can be manually run on any OpenTitan branch from the Actions tab.

[jwnrt]

@loiclefort and @rivos-eblot: This is Earlgrey only at the moment, but we can do the same with Darjeeling once we get proper support in the OpenTitan repo.

Let me know what you think of this approach. I don't want to slow down your Darjeeling QEMU work with Earlgrey problems. It runs against the earlgrey_1.0.0 branch where the hardware is frozen, so I don't expect regressions on the OpenTitan side.

[rivos-eblot]

Let me know what you think of this approach. I don't want to slow down your Darjeeling QEMU work with Earlgrey problems. It runs against the earlgrey_1.0.0 branch where the hardware is frozen, so I don't expect regressions on the OpenTitan side.

This approach seems ok to me and a great move toward a real CI, thanks.

[rivos-eblot]

This takes ~30 minutes at the moment.
Might be worth considering a local runner at some point (?)

[rivos-eblot]

Some suggestions

[AlexJones0]

Thanks @jwnrt, this looks all good from my side! (apart from the CI failure from the unsorted tests)