Tracking issue: grpc service tests

[grod220]

Objective: substantially add test coverage to our view & custody service tests.

View service

• Add tests for BalancesRequest
• Add tests for NotesRequest
• Add tests for NullifierStatusRequest
• Add tests for AddressByIndexRequest #397
• Add tests for AppParametersRequest #398
• Add tests for BroadcastTransactionRequest #400
• Add tests for EphemeralAddressRequest #401
• Add tests for FMDParametersRequest #402
• Add tests for IndexByAddressRequest #403
• Add tests for TransactionInfoByHashRequest #409
• Add tests for StatusRequest #405
• Add tests for NoteByCommitmentRequest #404
• Add tests for SwapByCommitmentRequest #407
• Add tests for AssetsRequest #399
• Add tests for StatusStreamRequest #406
• Add tests for AssetMetadataByIdRequest #506
• Add tests for TransactionInfoRequest #408
• Add tests for WalletIdRequest #411
• Add tests for GasPricesRequest #535
• Add tests for NotesForVotingRequest #536
• Add tests for UnclaimedSwapsRequest #538
• Add tests for WittnessRequest #539
• Add tests for OwnedPositionIdsRequest #537
• Add tests for TransactionPlannerRequest #410
• Add tests for WitnessAndBuildRequest #412

Custody service

• Add tests for AuthorizeRequest #413
• Add tests for ExportFullViewingKeyRequest #414

[grod220]

Likely many of these tests should be blocked by #312

[grod220]

Well done @Valentine1898!