rpc: Throw more user friendly arg type check error

Summary:

The arg type check error doesn't list which arg (position or name) failed. Fix that.

Backport of core#26929.

Due to out-of-order backports some tests have to be updated to account for the new error message.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D16314