Reland "Add flag to not close UDPSocket when we retry a write"

The original CL was reverted as it caused a lot of crashes due to
the socket being destroyed by the time we try to set the "don't close"
flag.

The diff from the original CL is that we set the "don't close" flag on
the socket before the asynchronous task is posted, rather than after.

Original change's description:
> Add flag to not close UDPSocket when we retry a write
>
> This CL adds a new flag to signify when a UDP socket should not be
> closed. This will help us investigate what is closing the socket
> unexpectedly.
>
> This is a temporary change and will be reverted once crash traces have been gathered.

> Bug: 1383390
> Change-Id: I2652321477535e4b092ddcb88f092ca27ac571a9
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4104688


> Reviewed-by: Adam Rice <ricea@chromium.org>
> Commit-Queue: Nidhi Jaju <nidhijaju@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1082983}

Bug: 1383390
Change-Id: Id719722ac8695bb51e8beeae6e6bad3e0a4c3db8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4560730


Reviewed-by: Adam Rice <ricea@chromium.org>
Commit-Queue: Nidhi Jaju <nidhijaju@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1148393}