Change ErrorKind::SemanticError to use Cow<'static, str> instead of &'static str (#356)

* Changed front::glsl::error::ErrorKind::Semantic to use Cow

* cargo fmt

* appeasing clippy

* Update src/front/glsl/functions.rs

Co-authored-by: monocodus[bot] <49363530+monocodus[bot]@users.noreply.github.com>

* Fixed more clippy errors

Co-authored-by: Dzmitry Malyshau <kvark@fastmail.com>
Co-authored-by: monocodus[bot] <49363530+monocodus[bot]@users.noreply.github.com>