Add 'cpp_info.<config>' information to 'cmake_find_package[_multi]' generators

[jgsogo]

Changelog: Fix: Add cpp_info.<config> information to cmake_find_package_multi and cmake_find_package generators.
Docs: conan-io/docs#1508

• At least update docs at "Note" here

Closes #6136

---

When a recipe contains information specific per configuration:

class Requirement(ConanFile):
    name = "requirement"
    version = "version"
            
    settings = "os", "arch", "compiler", "build_type"
            
    def package_info(self):
        self.cpp_info.libs = ["lib_both"]
        self.cpp_info.debug.libs = ["lib_debug"]
        self.cpp_info.release.libs = ["lib_release"]
                    
        self.cpp_info.cxxflags = ["-req_both"]
        self.cpp_info.debug.cxxflags = ["-req_debug"]
        self.cpp_info.release.cxxflags = ["-req_release"]

this information is now propagated to the corresponding build-type file (see tests)

[jgsogo]

• Order matters, who has precedence?

Check behavior of other generators:

CMake plain generators:

• cmake + TARGETS:

  set_property(TARGET CONAN_PKG::requirement PROPERTY INTERFACE_COMPILE_OPTIONS ${CONAN_C_FLAGS_REQUIREMENT_LIST} ${CONAN_CXX_FLAGS_REQUIREMENT_LIST}
                                                                $<$<CONFIG:Release>:${CONAN_C_FLAGS_REQUIREMENT_RELEASE_LIST} ${CONAN_CXX_FLAGS_REQUIREMENT_RELEASE_LIST}>
                                                                $<$<CONFIG:RelWithDebInfo>:${CONAN_C_FLAGS_REQUIREMENT_RELWITHDEBINFO_LIST} ${CONAN_CXX_FLAGS_REQUIREMENT_RELWITHDEBINFO_LIST}>
                                                                $<$<CONFIG:MinSizeRel>:${CONAN_C_FLAGS_REQUIREMENT_MINSIZEREL_LIST} ${CONAN_CXX_FLAGS_REQUIREMENT_MINSIZEREL_LIST}>
                                                                $<$<CONFIG:Debug>:${CONAN_C_FLAGS_REQUIREMENT_DEBUG_LIST}  ${CONAN_CXX_FLAGS_REQUIREMENT_DEBUG_LIST}>)
  

• cmake without TARGETS: it lets CMake use its defaults:

  macro(conan_set_flags build_type)
      set(CMAKE_CXX_FLAGS${build_type} "${CMAKE_CXX_FLAGS${build_type}} ${CONAN_CXX_FLAGS${build_type}}")
      set(CMAKE_C_FLAGS${build_type} "${CMAKE_C_FLAGS${build_type}} ${CONAN_C_FLAGS${build_type}}")
      set(CMAKE_SHARED_LINKER_FLAGS${build_type} "${CMAKE_SHARED_LINKER_FLAGS${build_type}} ${CONAN_SHARED_LINKER_FLAGS${build_type}}")
      set(CMAKE_EXE_LINKER_FLAGS${build_type} "${CMAKE_EXE_LINKER_FLAGS${build_type}} ${CONAN_EXE_LINKER_FLAGS${build_type}}")
  endmacro()
  

  There will be CMAKE_CXX_FLAGS, CMAKE_CXX_FLAGS_DEBUG and CMAKE_CXX_FLAGS_RELEASE, each one with its own variables.

• cmake_multi, generates only CONAN_*****_RELEASE/DEBUG variables, appending the Release/Debug info to the general one:

  set(CONAN_CXX_FLAGS_REQUIREMENT_RELEASE "-req_both -req_release")
  

  Then it uses the same TARGETS population and/or the same conan_set_flags function.

CMake find_package generators:

• cmake_find_package: doesn't use Release/Debug information
• cmake_find_package_multi: idem

---

[memsharded]

Looks perfect, can be merged.

[lasote]

Add docs and merge