Rename unconventional -> nonstandard, add config field
Add standard_macro_braces fields so users can specify macro names and
brace combinations to lint for in the clippy.toml file.
Fix errors caused by nonstandard_macro_braces in other lint tests
Fix users ability to override the default nonstandard macro braces
Add type position macros impl `check_ty`
This splits up the cast.rs tests and enables rustfix tests for the part
of the `unnecessary_cast` lint that emits `MachineApplicable`
suggestions.
cc #3630
