fix: split formulas into subdirectories

[mavogel]

Steps

• to avoid "formulae require at least a URL" error on M1 Pro Macbook #11
• revert dummy builds, e.g. fix(ci): add dummy arm build awsu#61
• add tests where we actually install the binaries on mac an ubuntu

Resources

• https://docs.brew.sh/How-to-Create-and-Maintain-a-Tap#external-commands