`_setValue` is now part of the controller's actor-facing surface: on the message
path a parent-side provider hook reaches it through `controller.input`, which
forwards to the real input as an `InvokeContentAction` message. The underscore
"internal, don't call from outside" convention no longer fits, so drop it.
Pure mechanical rename of the method on `UrlbarInput`/`SmartbarInput` and every
caller (`UrlbarProviderAutofill`, the test utils and tests), plus the message-
path `InputProxy` forwarder and its allowed-method set.
Differential Revision: https://phabricator.services.mozilla.com/D310364
Dão Gottwald
5bf1920e3f