Add diagnostic reporter function to lexer/parser and use that from mlir-opt to report errors instead of having the lexer/parser print the errors.
PiperOrigin-RevId: 201892004
Add parsing tests with errors. Follows direct path of splitting file into test groups (using a marker) and parsing each section individually. The expected errors are checked using FileCheck and parser error does not result in terminating parsing the rest of the file if check-parser-error.
This is an interim approach until refactoring lexer/parser.
PiperOrigin-RevId: 201867941
