feat(build): add arm64 support with cross-compilation

[gustavovalverde]

Motivation

To run dockerized containers in M1 and other ARM64 processors, we need to cross-compile the Docker image for this platforms. This makes it very hard to test locally, as all builds must be done remotely, or pushing to confirm on GHA.

This supersedes #3678
And reverts: #3791

Solution

Previously, we had to temporarily remove ARM64 support for Zebra until we could improve build times or have ARM64 instances to build it. Now that we're using Docker Build Cloud, we don't have to deploy ARM64 runners specifically for this task.

Tests

• Download the resulting artifact to an ARM64 machine and run it with docker, without using CPU virtualization.

Follow-up Work

• Must be done here: Update documentation for supported platforms.

PR Author's Checklist

• The PR name will make sense to users.
• The PR provides a CHANGELOG summary.
• [] The solution is tested.
• The documentation is up to date.
• The PR has a priority label.

PR Reviewer's Checklist

• The PR Author's checklist is complete.
• The PR resolves the issue.

[gustavovalverde]

We won't be able to do this until zcash/lightwalletd#476 is merged, and we don't have a deadline for that.