add boulder-mtca service

[jsha]

Includes a proto file with a service definition, an entry in startservers.py and consul.hcl, and configs in test/config and test/config-next (since startservers doesn't currently have a nice way for services to start only in config-next, particularly once boulder-ra starts depending on boulder-mtca in CI).

Also, fix a problem from #8764: the newly added field in orders was mtcaID but should have been mtcLogID.

[jsha]

Same issue as #8775: govulncheck is failing on Go stdlib functions because actions/setup-go doesn't know about the latest Go release. Evidently it checks https://github.com/actions/go-versions/blob/main/versions-manifest.json.

[github-actions]

@jsha, this PR appears to contain configuration and/or SQL schema changes. Please ensure that a corresponding deployment ticket has been filed with the new values.

[aarongable]

LGTM with some proto nits

[aarongable]

"ATM machine"

[jsha]

this is the future to which we are doomed. MT certificates feels wrong; "issues MTCs" is also ugly IMO. I think the path is to just make peace with saying ATM machine for the rest of our lives.

[aarongable]

Yeah, "issues MTCs" doesn't sound bad to me personally. I'd also be fine with it just saying "issues Merkle Tree Certificates", given that this is sorta the entry-point into documentation for this package.

But also none of this matters, the point of language is to communicate and the current version is clear.

[jsha]

One more proto update:

• not using checkpointSubtreeID yet, remove it
• Since we have mtcLogID in the response, mtcSerialNumber is somewhat redundant. Serial numbers contain log number as a prefix, and log IDs contain log number as a suffix. Use mtcEntryIndex instead.

[jsha]

Rebased on main after the digitalSignature change landed, and added one commit to tidy up some copy-pasted startup-order dependencies in startservers.py.