Bug 1610422 part 3. Pull in the missing upstream changes for RTCPeerConnection-createDataChannel.html. r=jgraham

The changes are as follows:

1. Add an id (and a change in the test label) in the test that now ends up

reading:

const channel = pc.createDataChannel('', { negotiated: true, id: 42 });

2. Add some whitespace bits.
3. Removes a bogus test (thus fixing bug 1550497). The test is bogus because null converts to 0 when converting to unsigned short, and that's a perfectly valid id value.

Compared to upstream, that leaves the following local changes:

• Tests for the "id in the unsigned short range, maybe invalid, but 'negotiated' not set" case.
• A clarification for one of the test descriptions.
• Tests for the "id out of the unsigned short range" case.

These changes are upstreamed in https://github.com/web-platform-tests/wpt/pull/21285

Differential Revision: https://phabricator.services.mozilla.com/D60472