chore: Revamp build system to overcome Cross issues

[diconico07]

What this PR does / why we need it:
This PR completely refactor the build system for akri, aiming to fix #656 :

• Rust components are now built within docker using XX for cross-compilation
• Made samples clear in a separate Makefile to ease with them getting out of the main repo soon
• Remove cross intermediate image
• Use buildx to build for multiple architectures
• Merge largely similar Dockerfiles
• Upgrade opcua-monitoring-broker to .NET 6 (part of Upgrade .Net Core 3.1 binaries to .Net 6 LTS or 7 #608)
• Upgrade opencv intermediate image to .NET 6 (the onvif broker still needs migration)

Special notes for your reviewer:

If applicable:

• this PR has an associated PR with documentation in akri-docs
• this PR contains unit tests
• added code adheres to standard Rust formatting (cargo fmt)
• code builds properly (cargo build)
• code is free of common mistakes (cargo clippy)
• all Akri tests succeed (cargo test)
• inline documentation builds (cargo doc)
• all commits pass the DCO bot check by being signed off -- see the failing DCO check for instructions on how to retroactively sign commits

[kate-goldenring]

Thanks for this amazing revamp! Great to see everything is building.

[kate-goldenring]

Thank you for revamping this. One ignorable nit on file rename but LGTM!

[bfjelds]

this is an incredible improvement!! super awesome.

from a quick glance, it looks like build times increase a bit ... if that's correct, i just want to make sure that isn't a problem for anything (this may be an outdated recollection, but i have vague memories about the test pipeline having a sleep to wait for some build part to finish: here).

maybe some of the .github/actions code can be removed as well?

[diconico07]

from a quick glance, it looks like build times increase a bit ... if that's correct, i just want to make sure that isn't a problem for anything (this may be an outdated recollection, but i have vague memories about the test pipeline having a sleep to wait for some build part to finish: here).

I increased the sleep you mentioned to be the maximum allowed run time for the build job, this way we are sure it won't cause any issue (also increased maximum run time for the run-test-cases job to take this change into account).
This can certainly be an argument to try to improve build time later on.

maybe some of the .github/actions code can be removed as well?

I forgot to remove them, they are all unneeded now, so they are all removed now.

[diconico07]

/version patch