Move m_orphan_work_set to net_processing

Summary:
This is a backport of core#19911 [2/6]
https://github.com/bitcoin/bitcoin/pull/19911/commits/8803aee66813d27ddbdfce937ab9c35f8f7c35bc
Depends on D10526

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10527