[clang][deps] Keep #pragma push_macro, pop_macro and include_alias when minimizing source code.

The #pragma directives push_macro/pop_macro and include_alias may influence the #include / import directives encountered by dependency scanning tools like clang-scan-deps.

This patch ensures that those directives are not removed during source code minimization.

Differential Revision: https://reviews.llvm.org/D112088