Changed API for remote services

[ChristianKuehnel]

After the comments on the PR in Home Assistant (home-assistant/core#12591), here's a proposal to a new API for the remote services:

• The call to e.g. trigger_remote_door_lock now blocks until we get a final answer from the server. Note: this might take some time.
• If the vehicle state is expected to change after the call: an update of the vehicle state is triggered after a call to the remote services.
• The account now offers a listener to subscribe to vehicle state changes. This is necessary so that we can notify all listeners after an updated is triggered by a call to a remote service
• I incremented the version number, as this is a breaking API change.
• Added horn and climate control as remote services. ⚠️ I could not yet test these on a live vehicle. It's just implemented after the other examples...
• Update to unit tests to cover the changed code.

[ChristianKuehnel]

@gerard33 please have a look at the changed API. It that what you and Martin discussed?

Right now I only implemented the synchronous case. I'm not sure if we want to add async as well...

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