fix(trusted_service): Resolve user ID in enableTrustedAccessibilityService

Certain AccessibilityManager callers have userId=USER_CURRENT
which needs to be resolved to a real user ID before acting on
the request.

Bug: 418057329
Test: verified by consumer of this API
Flag: android.view.accessibility.enable_trusted_accessibility_service_api
Change-Id: I7baa8cd4551bbd665d7acd8f25621f5fcbbff54b