Implement lexing and parsing for all WGSL number literal types (#1184)

* 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

Cargo.toml

@@ -28,6 +28,7 @@ serde = { version = "1.0", features = ["derive"], optional = true }
 petgraph = { version ="0.5", optional = true }
 rose_tree = { version ="0.2", optional = true }
 pp-rs = { version = "0.2.1", optional = true }
+hexf-parse = { version = "0.2.1", optional = true }
 
 [features]
 default = []
@@ -40,7 +41,7 @@ serialize = ["serde"]
 deserialize = ["serde"]
 spv-in = ["petgraph", "spirv", "rose_tree"]
 spv-out = ["spirv"]
-wgsl-in = ["codespan-reporting"]
+wgsl-in = ["codespan-reporting", "hexf-parse"]
 wgsl-out = []
 hlsl-out = []
 span = ["codespan-reporting"]