Fixes statsd returning too much data at once.

We observe a single ConfigMetricsReportList can be greater than the
safe size for the binder transaction buffer since we only check the
size of the current metrics in progress, but we also return the
previous reports stored on disk.

This change will attempt to send another ConfigMetricsReportList
as soon as possible if there's already a report on disk.

Also fixes a bug when trying to trigger data fetch before the client
has registered the corresponding dataFetchOperation.

Bug: 79201869
Test: Tested manually on marlin-eng
Change-Id: I2d3677162804a27e7a7a95d482d80c46bd994a67