Megaissue: improvements to WebSockets

[bignimbus]

### Tasks
- [ ] https://github.com/apollographql/apollo-kotlin/issues/2765
- [ ] https://github.com/apollographql/apollo-kotlin/issues/3020
- [ ] https://github.com/apollographql/apollo-kotlin/issues/4652
- [ ] https://github.com/apollographql/apollo-kotlin/issues/5217

[martinbonnin]

Closing as WebSocketNetworkTransport is shipped as part of 4.0.0-beta.6.
See #5862 for follow ups.

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