Apply DeviceConfig defaults before boot-time consumers

[pbzin]

Summary

• apply crDroid product DeviceConfig defaults when CustomDeviceConfigService starts
• start the service before network and other boot-time consumers read their flags
• retain the existing BOOT_COMPLETED reapply path

Root cause

CustomDeviceConfigService was started late and only applied defaults at BOOT_COMPLETED. Services initialized earlier could therefore cache upstream values for the entire boot even when a product supplied device_configs_override entries.

Validation

• verified product overrides are present before dependent boot services initialize
• retained the existing late reapply for consistency
• patch applies cleanly to current crDroid 16.0
• git diff --check