magnum: bump dependencies + modernize

[SpaceIm]

• relocatable shared libs on macOS: see [conan-center] Add a hook to check whether installed shared libs are relocatable on Linux & macOS hooks#376
• CMakeDeps support
• cache CMake configuration with functools.lru_cache
• use target glfw instead of unofficial glfw::glfw target
• reorder methods by order of execution
• bump vulkan-loader

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• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the conan-center hook activated.

[ghost]

I detected other pull requests that are modifying magnum/all recipe:

• [magnum] Modernize + add test for cmakedeps #8995

This message is automatically generated by https://github.com/ericLemanissier/conan-center-conflicting-prs so don't hesitate to report issues/improvements there.

[conan-center-bot]

All green in build 3 (0a1cc7f5c51d987afa936e64ddd59b86ff2b5f5f):

• magnum/2020.06@:
  All packages built successfully! (All logs)