feat(networkstream): per-connection process ref + process-aware batch key (SUB-7786)

The per-batch connection key was address/port/protocol with first-writer-wins,
so a second process connecting to the same endpoint was silently DISCARDED --
data loss, not merely misattribution. The same held for two processes resolving
one domain. The key now carries the process ref, so distinct processes coexist
while first-writer-wins is retained per process.

The ref is appended, never reordered: an unattributed key stays byte-identical
to the old format and can never collide with an attributed one. StartTimeNs is
boot-relative nanoseconds emitted verbatim; zero is legal pid-only identity.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Signed-off-by: Alon <alon@armosec.io>