test: use wait_for_{block,header} helpers in p2p_fingerprint.py

Summary:
This small PR takes use of the message receiving helper functions wait_for_block() and wait_for_header() in the test p2p_fingerprint.py. It also simplifies the checks for very old stale blocks/headers requests by getting rid of the functions last_block_equals() and last_header_equals() and rather only testing that no blocks/headers message is received at all. Unnecessary sending of requests are also removed and calls to time.sleep(...) substituted by ping syncs.

This is a backport of core#20047

Test Plan: ninja check-functional

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D10804