Performance: Optimize cross boundary call for codec.decode() error replace calls

[brittanyrey]

This is very similar to #156537. It removes the overhead of a cross boundary call per each char write. This change applies the same fix to a second call site in Modules/cjkcodecs/multibytecodec.c.

PR is already prepared.

Linked PRs

• gh-156745: Inline CJK replacement writer call #156744