chore: cherry-pick d5d222b6ca and 1627015c84 from webrtc

[ppontes]

[Merge M86] - Fix race with SctpTransport destruction and usrsctp timer thread.

The race occurs if the transport is being destroyed at the same time as
a callback occurs on the usrsctp timer thread (for example, for a
retransmission). Fixed by slightly extending the scope of mutex
acquisition to include posting a task to the network thread, where it's
safe to do further work.

Bug: chromium:1162424
Change-Id: Ia25c96fa51cd4ba2d8690ba03de8af9e9f1605ea
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/202560
Reviewed-by: Harald Alvestrand hta@webrtc.org
Commit-Queue: Taylor deadbeef@webrtc.org
Cr-Original-Commit-Position: refs/heads/master@{#33048}
No-Try: True
No-Presubmit: True
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/215101
Reviewed-by: Mirko Bonadei mbonadei@webrtc.org
Cr-Commit-Position: refs/branch-heads/4240@{#18}
Cr-Branched-From: 93a9d19d4eb53b3f4fb4d22e6c54f2e2824437eb-refs/heads/master@{#31969}

=============

[Merge M86] - Reland "Fix race between destroying SctpTransport and receiving notification on timer thread."

This reverts commit 8a38b1cf681cd77f0d59a68fb45d8dedbd7d4cee.

Reason for reland: Problem was identified; has something to do with
the unique_ptr with the custom deleter.

Original change's description:

Revert "Fix race between destroying SctpTransport and receiving notification on timer thread."

This reverts commit a88fe7be146b9b85575504d4d5193c007f2e3de4.

Reason for revert: Breaks downstream test, still investigating.

Original change's description:

Fix race between destroying SctpTransport and receiving notification on timer thread.

This gets rid of the SctpTransportMap::Retrieve method and forces
everything to go through PostToTransportThread, which behaves safely
with relation to the transport's destruction.

Bug: webrtc:12467
Change-Id: Id4a723c2c985be2a368d2cc5c5e62deb04c509ab
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/208800
Reviewed-by: Niels Moller nisse@webrtc.org
Commit-Queue: Taylor deadbeef@webrtc.org
Cr-Commit-Position: refs/heads/master@{#33364}

TBR=nisse@webrtc.org

Bug: webrtc:12467
Change-Id: Ib5d815a2cbca4feb25f360bff7ed62c02d1910a0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/209820
Reviewed-by: Taylor deadbeef@webrtc.org
Commit-Queue: Taylor deadbeef@webrtc.org
Cr-Commit-Position: refs/heads/master@{#33386}

TBR=nisse@webrtc.org

Bug: webrtc:12467
Change-Id: I5f9fcd6df7a211e6edfa64577fc953833f4d9b79
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/210040
Reviewed-by: Niels Moller nisse@webrtc.org
Reviewed-by: Florent Castelli orphis@webrtc.org
Commit-Queue: Taylor deadbeef@webrtc.org
Cr-Original-Commit-Position: refs/heads/master@{#33427}
No-Try: True
No-Presubmit: True
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/215060
Reviewed-by: Taylor deadbeef@webrtc.org
Commit-Queue: Mirko Bonadei mbonadei@webrtc.org
Cr-Commit-Position: refs/branch-heads/4240@{#19}
Cr-Branched-From: 93a9d19d4eb53b3f4fb4d22e6c54f2e2824437eb-refs/heads/master@{#31969}

Release Notes

Notes: Security: backported fix to chromium:1184441.

[release-clerk]

Release Notes Persisted

Security: backported fix to chromium:1184441.