Add the guidelines github workflow from app-boilerplate

[elric1]

We only had to make minor modifications to get this working. This first to note is that in their guidelines_enforcer.yml, we needed to specify that we build things from a subdirectory. After finding that config option, things are much easier.
They run clang --analyze, so we had to change a few remaining strcpy(3)'s into strlcpy(3).
And, we had to alter the app variant name to tezos_wallet and update the app flags to match what Ledger stores upstream in a DB that they maintain to doublecheck that you aren't changing this without filing a PR against said DB. We preserve the existing flags as specified in that DB, but we believe that the flags should be reviewed as:

• we are setting the flag to say that this is a library and it isn't [yet], and
• there are different flags on nanos than nanosp, nanox, and stax.

[emturner]

overall LGTM, but might want to see if we can wait until swap is merged, and then resurrect LedgerHQ/ledger-app-database#69

[elric1]

I've rebased this onto #19 because it makes more sense to do that. Let's review #19 first.

[elric1]

I took 8ed4e83: "In prep for scan-build, we eliminate use of strcpy(3)" out of this and put it in a separate pull request, #28. The PR will not succeed if #28 is not merged first as it solves a failure of one of the checks that these guidelines implement.

[elric1]

Had to rebase this onto #29, because we introduced an issue that broke the CI this introduces we then fixed in #29.