Replace direct reset with buffered writers

[korthout]

Description

This is a follow-up of #10018.

Chris wants to remove the reset method altogether. And once we have the new implementation, which is based on buffered writers, the reset will no longer be necessary, as creating a new ProcessingResultBuilder will also create a new, empty buffer

See #10018 (comment)

[menski]

@Zelldon is that something you would pick up while you are working on the buffered writers?

[Zelldon]

Yes @menski