[net processing] ignore unknown INV types in GETDATA messages

Summary:
Co-Authored-By: John Newbery <john@johnnewbery.com>

This is a backport of Core PR18808 [2/4]
https://github.com/bitcoin/bitcoin/pull/18808/commits/e257cf71c851e25e1a533bf1d4296f6b55c81332
Depends on D9084

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Differential Revision: https://reviews.bitcoinabc.org/D9084