Fold congestion control algorithms into tor-spec.txt

After we finalize the congestion control algorithms and parameter values for Prop324, we should merge them into tor-spec.

However, note that these won't be officially finalized until we confirm that Shadow has correctly predicted how the live network will behave. This won't happen until after live deployment. After live deployment, we will also remove unnecessary BDP and CC algorithms, as per #40566 (closed)

So what we actually need to specify won't include everything from the proposal.

Nick also requested that we cite the algorithms in the source code: !525 (comment 2776597)

We could cite the proposal first, and then update it for the final spec, or we could just wait to cite the spec.