* Migrate membership, nicks, scored-pool and session to decl_error * Fix tests * Update frame/scored-pool/src/tests.rs Co-Authored-By: Shawn Tabrizi <shawntabrizi@gmail.com> * Remove InsufficientBalance error from scored-pool * Replace Error::<Test, DefaultInstance> with Error::<Test, _> Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>