Rust: Add keywords & bytes, fix identifiers, and other improvements/fixes

Summary:
Changes:

• Add missing keywords.
• Remove obsolete types int & uint (these were depreciated by isize/usize): https://github.com/nox/rust-rfcs/blob/master/text/0544-rename-int-uint.md
• Remove type float, because it isn't a valid data type: https://doc.rust-lang.org/std/index.html#primitives
• Fix identifiers (entity rustIdent, marked with FIXME). The Rust identifier highlighting also detects Non-ASCII characters (in the Rust parser, an identifier is: [a-zA-Z\x80-\xff_][a-zA-Z0-9\x80-\xff_]*).

NOTE: The POSIX character class [[::ascii::]] is used. I don't know from which version of KTextEditor (or Qt) the use of POSIX character class is available, or if the use of this is a correct way. It works well, but if it isn't the correct way to do it, I can change it without any problem.

• Improved and fixes in the highlighting of numbers:
  • Add missing integer suffixes (i128, u128, isize, usize).
  • Add word border (\b) in numbers (Hex, Octal, Binary, Float, Decimal).
  • Improves float detection; floats with suffix 'f' are not allowed (only 'f32' & 'f64').
  • Highlight as 'Error' invalid numbers (Hexadecimal, Octal, Binary).
• Fix Raw Hashed Strings (r##"text"##). Before, only a maximum of 2 hashes are detected (this is mentioned in a comment). Now any number of #'s are allowed.
• Add byte characters & byte strings (b'X', b"XX", br"XX", br#"XX"#).
• Improves character detection and escape characters:
  • Highlight as 'Error' invalid characters.
  • Fixes unicode escapes: only the \u{NNNNNN} type is allowed (Not \uNNNN or \UNNNNNNNN).

NOTES:

• Binaries don't allow unicode escapes, so a difference is made between common and unicode escapes. The RegExpr rules used to detect escape characters are placed in the entities &commonEscape; and &unicodeEscape;.
• Escapes supported in: https://doc.rust-lang.org/std/primitive.char.html#method.escape_default

• The style of the itemData 'Scope' is changed from 'dsNormal' to 'dsProcessador', since the detection of identifiers was corrected.

I also added a test file. Any inconvenience or if I need to correct something, do not hesitate to notify!

Sources:

• Rust documentation: https://doc.rust-lang.org/
• Rust Playground: https://play.rust-lang.org/
• Rust in Vim: https://github.com/rust-lang/rust.vim/blob/master/syntax/rust.vim
• Rust in VSCode: https://github.com/Microsoft/vscode/blob/master/extensions/rust/syntaxes/rust.tmLanguage.json
• Rust in gedit: https://github.com/GNOME/gtksourceview/blob/master/data/language-specs/rust.lang
• Rust in ACE: https://github.com/ajaxorg/ace/blob/master/lib/ace/mode/rust_highlight_rules.js
• https://github.com/rust-lang/kate-config

Test Plan: I checked the modifications with the documentation and the compiler of Rust to avoid regressions.

Reviewers: dhaumann, cullmann

Reviewed By: dhaumann

Subscribers: kde-frameworks-devel

Tags: Frameworks, Framework: Syntax Highlighting

Differential Revision: https://phabricator.kde.org/D13498