Missing directory dependencies on CI

[samuelgruetter]

The end-to-end theorem that I'd like to sketch by the end of next week will introduce the following three dependencies which are currently not taken into account by the CI (where <-- means "depends on"):

• firmware/Hmac/HmacProperties.v <-- silveroak-opentitan/hmac/Spec/SHA256.v
• investigations/cava2/Sha256Properties.v <-- silveroak-opentitan/hmac/Spec/SHA256.v
• A file with an end-to-end theorem about Sha256, either living in firmware/Hmac (similarly to firmware/IncrementWait/IncrementWaitToCava.v), or in a separate directory <-- investigations/cava2/

To start, I can of course just build the right subdirectories locally & manually, but it would be nice if this was also supported on CI.

[jadephilipoom]

I suggest:

• Move investigations/cava2 out of investigations and make it a top-level directory that is run by CI
• Move the HMAC-specific circuit implementations out of cava2 and move it into a new directory silveroak-opentitan/hmac/hw (since we eventually want cava2 to be just the core library, it's probably good not to have a bunch of specific code there)
• Move the HMAC-specific firmware out of firmware and into a new directory silveroak-opentitan/hmac/sw (less sure of this one, but it might make sense to organize things by device for bigger projects like HMAC -- an unfortunate side effect is that the run_silicon_creator_tests_in_opentitan script will have to be copied)
• Move the end-to-end proofs into a new directory silveroak-opentitan/hmac/end2end
• Introduce the necessary CI dependencies:
  • silveroak-opentitan/hmac <-- cava2
  • silveroak-opentitan/hmac <-- firmware
• Remaining dependencies will be handled in silveroak-opentitan/hmac/Makefile:
  • silveroak-opentitan/hmac/hw <-- silveroak-opentitan/hmac/Spec
  • silveroak-opentitan/hmac/sw <-- silveroak-opentitan/hmac/Spec
  • silveroak-opentitan/hmac/end2end <-- silveroak-opentitan/hmac/hw
  • silveroak-opentitan/hmac/end2end <-- silveroak-opentitan/hmac/sw

We could also anticipate future slowness and separate the four silveroak-opentitan/hmac directories into their own CI jobs so that e.g. hw and sw can run in parallel.

[jadephilipoom]

Adding a note we talked about verbally during the project meeting: for #904, we should also preemptively introduce the CI dependency that firmware depends on cava2.

[jadephilipoom]

I think #910 resolved this one. We still might want to separate out the Util directory to further improve our dependency structure, but I think that's a separate improvement.