Fix: use self._run instead of self._conanfile.run to ensure vcvars apply for Ninja/NMake generators - #3803

follow up on #2803

when using ninja_installer/1.8.2@bincrafters/stable, right now the following code is required:

        if self.settings.compiler == 'Visual Studio':
            with tools.vcvars(self.settings, force=True, filter_known_paths=False):
                self.build_cmake()
        else:
            self.build_cmake()

I tried to simplify it in our zmq/4.2.2@bincrafters/stable recipe, but it currently fails, because there are places in CMake helper which use self._conanfile.run directly instead of self._run:

https://github.com/conan-io/conan/blob/1.8.3/conans/client/build/cmake.py#L183
https://github.com/conan-io/conan/blob/1.8.3/conans/client/build/cmake.py#L185

Changelog: Fix: vcvars is also called in the CMake() build helper when using Ninja or NMake generators.

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