ci(arm): Adds support for cross compilation and publishes Relay ARM docker images

[Dav1dde]

Updates the build/ci to support building multi arch docker images.

• Removes the now-unused docker images and build scripts, they are no longer used and we don't want to maintain them, they will eventually break.
• Uses regctl to transfer multi arch images directly between registries
• Fixes relay-debug.zip and relay.src.zip inconsistency

Future improvements:

• Add aarch64-apple-darwin to the matrix build
• Release aarch64 binaries on release builds
• Sign images (?)

I tested all modified workflows (like binary) and they still work:

• Release Binary
• DockerHub

As a goodie, the docker image pipeline should be a bit faster now when re-running (~ 5 minutes), cutting down on that total CI time :)

Closes: #1305

[olksdr]

Since in the description stays you tested the release workflows I have no other questions

great!

Once thing is left - try to deploy newly built image after this PR is merged and see that everything is still functioning as expected 😄

[olksdr]

so it does use qemu for something?

[Dav1dde]

Not 100% sure, I think buildx needs it to build the image, but the binary is compiled outside of the docker image, hence why it's almost instant.

[olksdr]

Do we already sign images?

[Dav1dde]

This is just so the regclient action checks the signature of the regclient binary, they had that in their readme and thought it was a good idea.