Optimize backslashreplace error handler

Optimize backslashreplace error handler

Issue #25318: Optimize backslashreplace and xmlcharrefreplace error handlers in
UTF-8 encoder. Optimize also backslashreplace error handler for ASCII and
Latin1 encoders.

Use the new _PyBytesWriter API to optimize these error handlers for the
encoders. It avoids to create an exception and call the slow implementation of
the error handler.