Merge branch 'trace-add-tracepoint-for-tcp_sendmsg_locked'

Breno Leitao says:

====================
trace: add tracepoint for tcp_sendmsg_locked()

Meta has been using BPF programs to monitor tcp_sendmsg() for years,
indicating significant interest in observing this important
functionality. Adding a proper tracepoint provides a stable API for all
users who need visibility into TCP message transmission.

David Ahern is using a similar functionality with a custom patch[1]. So,
this means we have more than a single use case for this request, and it
might be a good idea to have such feature upstream.

Link: https://lore.kernel.org/all/70168c8f-bf52-4279-b4c4-be64527aa1ac@kernel.org/
v2: https://lore.kernel.org/20250407-tcpsendmsg-v2-0-9f0ea843ef99@debian.org
v1: https://lore.kernel.org/20250224-tcpsendmsg-v1-1-bac043c59cc8@debian.org
====================

Link: https://patch.msgid.link/20250408-tcpsendmsg-v3-0-208b87064c28@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>