log: Nuke error(...)

Summary:
error(...) has many issues:

• It is often used in the context of return error(...), implying that it has a "fancy" type, creating confusion with util::Result/Error
• -logsourcelocations does not work with it, because it will pretend the error happened inside of logging.h
• The log line contains ERROR: , as opposed to [error], like for other errors logged with LogError.

Fix all issues by removing it.

This is a backport of core#29236

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D18977