Auto merge of #29710 - servo:rename_sender_receiver_in_constellation, r=mrobinson

Make names of Sender<> and Receiver<> variables more coherent

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Sometimes these variables are called port, sometimes ipc, sometimes they have the name of the thread on the other end and sometimes not.  This PR tries to standardize on an obvious name for all of them:

Common pattern to note in this PR:
- If it is a `IpcSender`, then naming is followed by `ipc_sender`, such as:  `bluetooth_ipc_sender`,  `canvas_ipc_sender` etc..
- If variable is `crossbeam_channel` sender/receiver then naming is followed by `sender`/`receiver` such as:  `devtools_sender`, `canvas_sender` etc...

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix [#29679](https://github.com/servo/servo/issues/29679)

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- [ ] There are tests for these changes OR
- [x] These changes do not require tests

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