Purpose

Change to be using github actions instead of jenkins
This is supposed to be a big bang integration with no expectation on keeping jenkins builds alive, should we encounter issues then we revert this PR.
I am not changing the current workflows unless errors exists.

Changes

Two different releases, namely rc and alpha. Furthermore using workflow dispatch one can build an individual artifact or image.
Alpha releases: macOS, Windows, Ubuntu stagenet, Docker stagenet, bootstrapper, and the database exporter.
Rc releases: Everything
Making individual build be using --release
Move into build variable definition into the caller
Use prebuilt binaries on linux instead of building it for flatbuffers

TODO

Validate artifact and images:

• macOS
• Windows
• Ubuntu stagenet
• Ubuntu testnet
• Ubuntu mainnet
• Ubuntu flynet
• Bootstrapper
• Database exporter
• Docker stagenet
• Docker testnet
• Docker mainnet

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.