C++20 compatibility fix for regor logging

Logging dependency fmt::format takes fstring as input by default, which is required to
return compile time constant expression when built with C++20 (enforced by C++20 specifier
consteval). To make the logging work with C++20, the string input needs to be converted
to runtime evaluated string expression via fmt::runtime first.

Also fix minor bugs in tflite_model_semantics.cpp that causes build to fail with C++20.

Signed-off-by: Limin Tang <limintang@meta.com>