Use char_traits for case insensitive comparison

[bradallred]

see FIXMEs from ceb77ab. We need to be able to operate on a range of bytes, regardless of the presence of '\0' characters.

We need to create a std::char_traits like class for handling case insensitive comparison. Something like this.

The CstrHash, CstrLess, and CstrEq templates need to change their implementation to use traits instead of a string comparison function.

Likewise, StirngView and FixedSizeString both ought to have a template parameter for this and implement all comparisons through it.

[bradallred]

IDSImporter can also leverage this to shed a bunch of stricmps.