[stdlib] Introduce Hasher type with all necessary changes

[mzaks]

This is a draft because although the code compiles 8 tests are failing. It might be due to compiler bug. The error messages are cryptic. I don't have the "Mojo" ;) to fix them.

Failed Tests (8): Mojo Standard Library :: builtin/test_dtype.mojo Mojo Standard Library :: builtin/test_hash.mojo Mojo Standard Library :: builtin/test_object.mojo Mojo Standard Library :: builtin/test_string.mojo Mojo Standard Library :: builtin/test_string_literal.mojo Mojo Standard Library :: collections/test_dict.mojo Mojo Standard Library :: collections/test_set.mojo Mojo Standard Library :: python/test_python_object.mojo