Compile smaller libraries (now we are compiling Poco)

[jgsogo]

Smaller libraries, less time... and they use CMake/Meson/... the same way

[memsharded]

Compiling Poco was also a way to validate that OpenSSL and Zlib packages are also working, which is more comprehensive than just testing building a library with CMake. I agree something smaller and faster to compile would be nicer though.

We should probably also separate intensive tests of these repo from tests of packages in ConanCenter.