[upstream] Rebase OpenTitan Implementation to QEMU 10.2

[moidx]

Rebase against https://github.com/qemu/qemu/tree/v10.2.0

[jwnrt]

I've merged the 10.2.0 changes and updated the default branch here. We don't see any regressions from 10.1.0.

[luismarques]

https://github.com/lowRISC/qemu/tree/ot-10.2.0

[jwnrt]

I've prepared some commits which build up our fork on upstream 10.2.0, you can see them as a pull request here: #322

@amit-kumarh please let me know if the granularity is what you expect. I've split the commits in a way that I think is easier to rebase and resolve conflicts, not to make them small/reviewable. All the OpenTitan blocks (and both machines) are added in a single commit because they don't collide with anything in the upstream repo.