Use Conan 2

[johannes-wolf]

Use Conan 2 for package management.

Emscripten + Node.js get installed via Conan. There is currently a problem of Conan packages not allowing to override their tool-requirements, so we install nvm and node.js v21 in the build-ui.bash script into a temporary directory to force override the node version Conan installs for us (which is too old for angular). See: conan-io/conan-center-index#23088.

This also fixes problems with conflicting CMake targets from cesium by building cesium as an external project (see cmake/cesium.cmake).

The cross-build is set up using a Conan profile.

• Publish mapget to conan.io and use it from there

[johannes-wolf]

Waiting for emsdk linux64 build clarification.

[johannes-wolf]

@Waguramu @josephbirkner, do we have some (new) minimum version requirements on emsdk Node.js durring build? These build errors appeared after rebasing this PR on master.

[josephbirkner]

@Waguramu @josephbirkner, do we have some (new) minimum version requirements on emsdk Node.js durring build? These build errors appeared after rebasing this PR on master.

Yes, we upgraded to 3.1.56 due to this: emscripten-core/emscripten#21460

[johannes-wolf]

Ok. Conan has no emsdk > 3.1.50 yet, so we either have to wait or get conan to use the hosts emsdk. I will have a look into the second option later; there is something like [system_requires].

[MisterGC]

This PR is no longer relevant, as there is no demand for Conan and it just causes a development overhead (e.g. regarding emscripten or dependency management of Cesium) - we will reconsider the support on demand.