Implement more core operations and documentation tests

[udoprog]

Changelog notes:

Added

• We can now run documentation tests, and this has been leveraged to verify the behavior of many more std operations.

Changed

• Integer types have been rename to match their rust equivalents:
  • byte is now named u8.
  • int is now named i64.
  • float is now named `f64.
• As a result of the above, some module renames have taken place:
  • std::int module has been renamed std::i64.
  • std::float module has been renamed std::f64.
• Literal operators with type hints are now supported:
  • 10u8 would correlate to a byte, which is now known as u8.
  • 10i64 would correlate to an int, which is now known as a i64.
  • 10f64 would correlate to a float, which is now known as a f64.
• Coerce operator <value> as <type> is now supported, such as: 1u8 as f64. It's behavior matches exactly that of Rust.