FontInfoBase and it's descendents are missing noexcept annotations, which
virally forces other code to not be noexcept as well during AuditMode checks.
Apart from adding noexcept, this commit also
* Passes std::wstring_view by reference.
* Pass the FillLegacyNameBuffer argument as a simple pointer-to-array,
allowing us to fill the buffer with a single memcpy.
(gsl::span's iterators inhibit any internal STL optimizations.)
* Move operator== declarations inside the class to reduce code size.
All other changes are an effect of the virality of noexcept.
This is an offshoot from #11623.
## Validation Steps Performed
* It still compiles ✔️
95cc7d9625