[net] Move RecordBytesSent() call out of cs_vSend lock

Summary:
[net] Add cs_vSend lock annotations

This is a backport of core#20816

Test Plan:
With TSAN and Debug

ninja all check check-functional

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13268