Fix build breaks from llvm-17 (#461)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/461

Clang-17 is stricter around format strings and ambiguous headers.
* Cast the enums to the right format type
* Namespace `format_to` methods with `fmt` since libc++ 17 introduces its own std::format

Reviewed By: lanza

Differential Revision: D49556599

fbshipit-source-id: eb9ebed3aa1bac844dac83dc5b0118106978a839