Replace a few cases of `Thread* const` with `TaskQueueBase* const`

Update member variables and constructor arguments in a few classes,
including `RtpSender`, `JsepTransport`, and `FifoBuffer`, to use
`TaskQueueBase*` instead of `Thread*`.

This change narrows the interface exposed to these classes. Since
`Thread` inherits from `TaskQueueBase`, using the base class restricts
access to `Thread`-specific methods like `BlockingCall()`. This helps
enforce asynchronous patterns, isolates where blocking calls are
currently permitted, and prevents the introduction of new synchronous
calls in these contexts.

Update `BUILD.gn` files to replace dependencies on `rtc_base:threading`
with `api/task_queue` where appropriate.

Bug: none
Change-Id: I6d666066eaeb1efb45bf4a7aec12ea448c21baa2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/425120
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#46176}