Add RAW_STRING_LITERAL

[AnshVM]

Add RAW_STRING_LITERAL token variant and the LitType::RAW_STRING variant.

gcc/rust/ChangeLog:

* ast/rust-ast-collector.cc (TokenCollector::visit): Handle RAW_STRING case in TokenCollection::visit
* ast/rust-ast.cc (AttributeParser::parse_meta_item_inner): Add RAW_STRING_LITERAL case to call parse_meta_item_lit() (AttributeParser::parse_literal): Add RAW_STRING_LITERAL case.
* ast/rust-ast.h: Add RAW_STRING_LITERAL to is_stirng_lit(). Add RAW_STRING enum variant to LitType enum.
* hir/rust-ast-lower-base.cc (ASTLoweringBase::lower_literal): Handle raw string literal type, falls back to rust_unreachable() for now.
* lex/rust-lex.cc (Lexer::parse_raw_string): Use make_raw_string instead of make_string.
* lex/rust-token.cc (Token::as_string): Handle case for RAW_STRING_LITERAL.
* lex/rust-token.h (enum PrimitiveCoreType): Add RAW_STRING_LITERAL token type. Define make_raw_string function to create RAW_STRING_LITERAL token. Add RAW_STRING_LITERAL case to is_literal().
* parse/rust-parse-impl.h (Parser::parse_attr_input): Handle case for RAW_STRING_LITERAL. (Parser::parse_literal_expr): Handle case for RAW_STRING_LITERAL (Parser::parse_pattern_no_alt): Handle case for RAW_STRING_LITERAL

[CohenArthur]

LGTM

[P-E-P]

PR is great, changelog is here but we're missing DCO (you can git commit --amend -s to add it).

Unless you're part of the fsf list but I don't know where it could be found and thus cannot verify (@CohenArthur do you know?).

[CohenArthur]

some people can access it but I can't. weird that our CI setup does not catch anything... but yes good point @P-E-P, you need to sign your commit @AnshVM

[AnshVM]

Thanks for pointing that out @P-E-P
Signed my commit 👍