fix: INSTALL.md can now be followed to install grSim on macOS.

[Leikoe]

Identify the Bug

grSim cannot be installed currently on macOS by following INSTALL.md

#176

Description of the Change

removed legacy protocolbuffers cmake api usage, now grSim can build using brew install protobuf@21, still doesn't build with latest because of a problem with abseil, protobuf 21 doesn't use abseil. And updated INSTALL.md

Alternate Designs

tried to follow as closely the current CMakeLists.txt structures, could have updated them to build a separate object as the protocolbuffers example usage suggests https://github.com/protocolbuffers/protobuf/blob/main/docs/cmake_protobuf_generate.md

Possible Drawbacks

Verification Process

need to be tested on other OS, works on macOS sonoma with protobuf@21 installed via brew.

Release Notes

FIX - INSTALL.md can now be followed to install grSim on macOS.

[g3force]

I've updated the GitHub action pipelines and updated your branch.

Looks like is not working for Linux anymore ;)

Can you make sure that it is working for both Ubuntu versions again at least?
The other jobs are also still failing on master. I hoped that with your changes, the macos-12 and windows jobs would be fixed.

[Leikoe]

sadly, ubuntu 22.04 is still using protobuf 3.12, latest ubuntu should be able to compile this

[g3force]

Why do you need the recent protobuf version for macos?
Ubuntu 22.04 is still the latest LTS version, so it must work with that. And preferably also with the previous LTS version, 20.04.
Would it be possible to install an older version with brew, if there are breaking changes?