Fix truncated NetLogs by introducing the --net-log-duration
flag.

Net logs generated via the command line were often
truncated due to insufficient mechanisms to catch
close event.This change introduces the --net-log-duration
flag,which specifies the duration (in seconds)
for network logging. When provided with a positive
integer X, Browser will automatically stop logging
after X seconds and flush the complete NetLogs to disk.

Bug: 40283474
Change-Id: Ia958aae8caae4ffcfcfc78ce0e19516fcbaf4006
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6293542
Reviewed-by: Andrew Williams <awillia@chromium.org>
Commit-Queue: krishna dheeraj Pannala <kpannala@microsoft.com>
Reviewed-by: Adam Rice <ricea@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1431364}