[GL] Use StringView instead of std::string

[st0rmbtw]

This PR is not much useful, just some code quality changes.

I'm not sure if I've done it right, but in theory it should reduce the amount of string copies.

[LukasBanana]

Looks like a neat improvement. Once StringLiteral was introduced in the public interface, all those std::string instantiations become merely transition variables that pass on their internal data but don't need to own the memory, so this change makes perfectly sense.

Please be so good and wrap all the nameLength into static_cast<std::size_t> to make the type conversion from GLint and GLsizei explicit. I was suprised the compilers don't warn, but I presume that's only happening on a higher warning level.

[st0rmbtw]

I polluted the branch, so I created a new branch in my local fork, cherry-picked those two commits into that branch and forced pushed them into this remote branch.

Please, check if I've done it right.

[LukasBanana]

Looks good to me. I'll merge as soon as the unit tests succeed. GitHub has the Squash and merge operaton, so it shouldn't matter how many commits you pushed.