univalue: Return more detailed type check error messages

Summary:
Print the current type and the expected type

Backport of core#25629.

Depends on D16282.

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D16283