CI: Test on MacOS and Linux ARM64 / Aarch64 (#524)

* CI: add Linux ARM64

* CI: explicit permissions

* CI: use actions/cache@v4 (v2 is deprecated on Feb 1st, and v3 was supposed to be as well)

* CI: use ARM builder images revert version spec change (was working on something in parallel)

* CI: remove TEST_LANG option to build with cpp

* CI: revamp installer to support ARM

* CI: GMP not in PATH on newer MacOS

* CI: GMP not in MacOS path, manually do the C integration tests

* CI: run 10% less tests in CI

* CI: Go/Rust uses default (with assembly)

* CI: MacOS run C tests

* CI: move and polish install_nim.sh, fix MacOS using msys2