Archive downloads and omc files

[AnHeuermann]

It should be possible to save e.g. the Windows installer or the programs installed by apt between runs to speed up setup time of setup-openmodelica for the next run.

• Cache Windows installer
• Cache installed OpenModelica on Windows
• Cache installed apt package on Linux

[AnHeuermann]

See https://github.com/actions/toolkit/tree/main/packages/cache