Move SyntaxShape specifier parsing into own file (#10448)

Pure move refactor.

Followup to:
- #10511
- #10512
- #10544 
- #10548 
- #10581

crates/nu-parser/src/lib.rs

@@ -5,6 +5,7 @@ mod lex;
 mod lite_parser;
 mod parse_keywords;
 mod parse_patterns;
+mod parse_shape_specs;
 mod parser;
 mod parser_path;
 mod type_check;