[Settings] Access ProxySubscriptionManager within DataUsage

Redirect some SubscriptionManager access to ProxySubscriptionManager.
This will reduce some access latency.

Bug: 141833767
Test: manual
Test: m RunSettingsRoboTests -j ROBOTEST_FILTER=DataUsageSummaryPreferenceControllerTest
Change-Id: I2cb30dd0570a09543a13ca01cf054ba2d18d70d4
2 files changed