StatsManager throws exceptions

When StatsManager fails to connect to statsd, it now throws an exception
for the caller to catch. It also throws an exception of the config being
added is of an unreadable format.

Due to backwards compatibility issues, the old APIs could not be
changed, so new ones were made to replace the old ones. The old ones are
now temporary and will be removed when the compatibility issue is
resolved.

Bug: 77648233
Test: gts-tradefed run gts-dev --module GtsStatsdHostTestCases
Change-Id: Ibea05883a29b9b3ef9927d2f8fe295eb99832ab7