Set audiostreamplayer default area_mask to 0 and exit early to reduce performance overhead.

[pirey0]

Addresses #106751

Quick summary:
By default AudioStreamPlayers2D/3D do a physics check on their position every frame when running to support the audio_bus_override feature on Area2D/3D.

From my search this is a feature that is rarely used, but results in a non negligible overhead for all projects, even if the feature is never used.

I propose setting the default area_mask to 0 and exiting early in those scenarios to remove this overhead.

Reasons:

1. Most projects don't use this feature and should thus not be affected by the cost.
2. A default of 0 (aka. no overlap) more closely aligns with the opt-in nature of the feature.
   I think the default of 1 (aka. check for overlaps with all default areas) is more likely to cause unexpected behaviour.
3. Most projects using this feature will very likely be using a specific non-1 layer for this effect and will thus be unaffected by the change.

Warning:

This PR includes a Behavior Breaking Change:
Projects using the audio_bus_override feature on the default layer will find their overrides not working anymore.
(Though I expect this number to be very low, can do a targeted search if required)