Rewrite the new attribute parser

Author: JonathanBrouwer

compiler/rustc_attr_parsing/messages.ftl

@@ -182,3 +182,10 @@ attr_parsing_invalid_attr_unsafe = `{$name}` is not an unsafe attribute
     .label = this is not an unsafe attribute
     .suggestion = remove the `unsafe(...)`
     .note = extraneous unsafe is not allowed in attributes
+
+attr_parsing_invalid_meta_item = expected a literal (`1u8`, `1.0f32`, `"string"`, etc.) here, found {$descr}
+    .remove_neg_sugg = negative numbers are not literals, try removing the `-` sign
+    .quote_ident_sugg = surround the identifier with quotation marks to make it into a string literal
+
+attr_parsing_suffixed_literal_in_attribute = suffixed literals are not allowed in attributes
+    .help = instead of using a suffixed literal (`1u8`, `1.0f32`, etc.), use an unsuffixed version (`1`, `1.0`, etc.)