Improve errors for `generate_solution_type` macro (#9553)

* add more errors for check attributes in npos elections solution type

* revert local env

* return Ok false if there are no attributes

* fmt

* Update primitives/npos-elections/solution-type/src/lib.rs

Co-authored-by: Squirrel <gilescope@gmail.com>

* Update primitives/npos-elections/solution-type/src/lib.rs

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* Update primitives/npos-elections/solution-type/src/lib.rs

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* Update primitives/npos-elections/solution-type/src/lib.rs

* improve span by giving extra attribute, nightly fmt

* fix test to test new error msg

Co-authored-by: Squirrel <gilescope@gmail.com>
Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>