Naming conventions for properties in returned objects

In #12840, @ddbeck and @foolip had been discussing a convention for the properties in the objects returned by certain methods. Quoting the conversation here:

Since we don't have a guideline, maybe this is an opportunity to start from scratch? How about returns_audioCapabilities_property with the idea being that we could have a convention for object properties (like this one), types (like returns_DOMMatrix_type), and values (like returns_undefined_value).

We should probably put the word return in the description too. Returns <code>audioCapabilities</code> property?

Originally posted by @ddbeck in https://github.com/mdn/browser-compat-data/pull/12840#discussion_r752159554

More ideas on these lines, to cut down on the wordiness:

• audioCapabilities in return value object
• audioCapabilities in returned object
• Returns object with audioCapabilities
• Returns object with audioCapabilities property

Originally posted by @ddbeck in https://github.com/mdn/browser-compat-data/pull/12840#discussion_r760983814

This made me think of the possibility of %parameter%_property_returned as the standard key, if that sounds nice?

No files or tests are named. Start by reading issue #12840 and the quoted discussion about returned-object properties, then identify the existing conventions and affected keys; done means the naming convention is settled and its scope is documented.