[feature] Recognize Clang CL on Windows as tool method

[uilianries]

Just like is_msvc, usually, in CCI, we need to use the follow idiom to check when running clang-cl:

@property
def _is_clang_cl(self)
    return (self.settings.os == "Windows" and self.settings.compiler == "clang") or \
            self.settings.get_safe("compiler.toolset") == "ClangCL"

It would be great internalizing it as part of conan.tools.microsoft so we no longer need to copy/past that method.

You can find its usage by the follow search: https://github.com/conan-io/conan-center-index/search?q=_is_clang_cl

• I've read the CONTRIBUTING guide.

[uilianries]

The feature will not be merged.