Investigate and removed fixed length strings in the loader

[charles-lunarg]

The loader shouldn't use fixed length strings in most places as not everywhere has a mandate that the length of a string is arbitrarily limited (unlike layer & extension names which are).

This issue is both an exploratory issue to find possible instances of fixed length strings and to fix them.

[charles-lunarg]

This would help a small amount in the performance department as the loader spends a non-trivial amount of time mem-setting strings to zero which isn't necessary if strings were only as long as they needed to be.