WASM griddly tests configuration

[maichmueller]

This PR configures CMake to build the griddly tests also for the WASM build.

Adds:

• Cmake target building of griddly_tests with WASM
• Includes macros for test files to conditionally remove WASM incompatible code segments (e.g. Vulkan related parts)
• Adapt conanfile_wasm to import the necessary griddly libs for wasm as well.

TODO:

• Add wasm griddly_test execution to github actions workflow (intentionally left out due to existing issue)

[maichmueller]

Merge should ensure #288 has been addressed.