Update Dockerfile and add Actions workflow to build it

[elopez]

This PR:

• updates the Dockerfile base to Ubuntu Jammy (22.04)
• separates build and install processes into two stages
• replaces fixed solc binary with solc-select
• adds a workflow that builds the container for
  • linux/amd64 (x86_64 systems),
  • linux/arm64 (ARM 64-bit systems, eg. Mac M1 with Docker Desktop)
  • linux/arm/v7 (ARM 32-bit systems, eg. some SBC systems)
• publishes the container on GHCR:
  • matching tagged builds for tag releases,
  • edge tag matching the latest master commit
  • latest tag matching the latest release
  • testing-foo matching the latest commit in branch foo (must be also enabled in the workflow on: .. section)

Closes: #937, #1330