* Implement lexing for all WGSL number literal types

* Move number literal test cases

* Adjust tests to match WGSL spec on number literals

Suffixes are not type names and currently only a plain `u` is supported
for uints. More specifically, `i` and `f` suffixes or suffixes with
widths in bits like `u32` are not supported at the moment.

* Add more tests for invalid number literal suffixes

* Replace code too new for Rust 1.43

* Implement parsing for hexadecimal integers

* Switch to enum number types, and Bytes for width

* Check for negative and leading zeros in int literals

* Implement parsing of hex floats with hexf-parse

* Update error message tests

* Update snapshot test output files

* Clean up lexer state machine code

* Clean up unexpected token error code

* Move number literal parsing to own submodule