[mlir][python] Implement more SymbolTable methods.

* set_symbol_name, get_symbol_name, set_visibility, get_visibility, replace_all_symbol_uses, walk_symbol_tables
* In integrations I've been doing, I've been reaching for all of these to do both general IR manipulation and module merging.
* I don't love the replace_all_symbol_uses underlying APIs since they necessitate SYMBOL_COUNT walks and have various sharp edges. I'm hoping that whatever emerges eventually for this can still retain this simple API as a one-shot.

Differential Revision: https://reviews.llvm.org/D114687