Add file to configure Conan as a cmake dependency provider

[jcar87]

• Add conan_provider.cmake with logic to call CMake's SET_DEPENDENCY_PROVIDER - note that we could reuse conaninstall.cmake and do it there directly.
• Amend tests to pass conan_provider.cmake via CMAKE_PROJECT_TOP_LEVEL_INCLUDES
• Add logic to handle CMake -> conan compiler name for Apple Clang
• Add logic to handle figuring out where the generated files end up at (since this depends on the layout defined, if one is defined)
• Add logic to persist that directory across CMake runs (as conan is only invoked once).

[CLAassistant]

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