dtls-in-stun: fix DTLS 1.x resend/acking behavior

This patch does "the same" as https://webrtc-review.git.corp.google.com/c/src/+/450983
with the following noticeable changes
- handle both 1.2 & 1.3 !
- add unit test
- use dtls/srtp as a signal for then peer is also writable
as show by https://webrtc-review.git.corp.google.com/c/src/+/449762,
(note: it use existing callbacks rather than adding a new!).

Bonus!
1) fix bug in callback_list when removing from list
during callback, add new testcases that failed before change in this.
2) address most of comments added late to https://webrtc-review.git.corp.google.com/c/src/+/449561

Bug: webrtc:367395350
Change-Id: I131ba3ac920187bc9dec004ba55e297540ddf27c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/451521
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Commit-Queue: Jonas Oreland <jonaso@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#46976}