Add FastPairTestDataProviderService#onManageFastPairAccountDevice logging.

FastPairAccountKeyDeviceMetadata do not support toString(),
this change log it as JSON string.
This change also resolve Kotlin list problems.

Test: go/ml-fp-dp-tool with NearbyFastPairProviderSimulatorApp
Bug: 214015364
Ignore-AOSP-First: nearby_not_in_aosp_yet
Change-Id: I039a58ecb6c8212b69ff4305b23793b168f08f66
2 files changed