fix: WebRTC transport unhandled promise rejection during connect

[achingbrain]

Simplifies the connection logic to just use the abort signal to abort the dial instead of the abort signal and multiple deferred promises.

Fixes a crash in node where the abort signal passed into a WebRTC private to private dial can cause an unhandled promise rejection due to a race condition between the abort firing and awaiting the connectedPromise promise:

file:///Users/alex/Documents/Workspaces/ipfs/helia-http-gateway/node_modules/@libp2p/webrtc/dist/src/private-to-private/initiate-connection.js:42
            connectedPromise.reject(new CodeError('SDP handshake aborted', 'ERR_SDP_HANDSHAKE_ABORTED'));
                                    ^

CodeError: SDP handshake aborted
    at EventTarget.sdpAbortedListener (file:///Users/alex/Documents/Workspaces/ipfs/helia-http-gateway/node_modules/@libp2p/webrtc/dist/src/private-to-private/initiate-connection.js:42:37)
    at [nodejs.internal.kHybridDispatch] (node:internal/event_target:807:20)
    at EventTarget.dispatchEvent (node:internal/event_target:742:26)
    at abortSignal (node:internal/abort_controller:369:10)
    at AbortController.abort (node:internal/abort_controller:391:5)
    at EventTarget.onAbort (file:///Users/alex/Documents/Workspaces/ipfs/helia-http-gateway/node_modules/any-signal/dist/src/index.js:8:20)
    at [nodejs.internal.kHybridDispatch] (node:internal/event_target:807:20)
    at EventTarget.dispatchEvent (node:internal/event_target:742:26)
    at abortSignal (node:internal/abort_controller:369:10)
    at AbortController.abort (node:internal/abort_controller:391:5) {
  code: 'ERR_SDP_HANDSHAKE_ABORTED',
  props: {}
}

Node.js v20.8.0

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if necessary (this includes comments as well)
• I have added tests that prove my fix is effective or that my feature works

[maschad]

The refactor makes sense , but are you able to simulate this race condition?

[achingbrain]

I've added a test that fails against main and also causes a PromiseRejectionHandledWarning to be logged:

(node:24480) PromiseRejectionHandledWarning: Promise rejection was handled asynchronously (rejection id: 33)
(Use `node --trace-warnings ...` to show where the warning was created)