Implement string and integral formatters without IO streams

The goal is for BasicStringFormatter to not depend on IO streams at all.
IO streams are inherently slow due to localization.

With C++20, std::to_chars can be used to convert arithmetic types to
strings. However, major compilers do not yet support std::to_chars for
floating point types.

There's probably plenty of room here for optimizations, but this is a
good enough start to removing IO streams.

Further, with this implementation, string and integral types now support
center alignment. Floating point types will still fall back to default
alignment.

Author: trflynn89