Use absl::AnyInvocable instead of std::function in RtpTransceiver

This change updates pc/rtp_transceiver.h to use absl::AnyInvocable
instead of std::function  for callbacks.

This aligns with webrtc guidance:
https://webrtc.googlesource.com/src/+/refs/heads/main/g3doc/style-guide.md

This change was made by Gemini with the following prompt:
Use commit d471f7cf9a3e7900404ba5ef1 as a template for how to port each use of std::function in the `pc/rtp_transceiver.h` file to absl::AnyInvocable.
Use absl::AnyInvocable<void() &&> for callbacks used once and absl::AnyInvocable<void()> otherwise.
Port usage one at a time and use `ninja -C out/Default` to see if you change compiles before moving to the next.
Use `git cl format` to ensure formatting.
Use `git diff --name-only | xargs tools_webrtc/iwyu/apply-include-cleaner` to add include files needed.
Use `tools_webrtc/gn_check_autofix.py -C out/Default` to update the BUILD.gn files.
Create a commit message in the same style as the commit above.

Bug: none
Change-Id: Ida3dbb3b6a34d3f365d057b8a23a8151392a6155
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/425100
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Philipp Hancke <philipp.hancke@googlemail.com>
Cr-Commit-Position: refs/heads/main@{#46175}