Problem
Slot status can be used of in other scenarios in addition to account information such as transactions, blocks. The current implementation is too tightly coupled.
Summary of Changes
Decouple the slot status notification from accounts notification. Created a new slot status notification module.
Use bulk insertion to Postgres at startup to reduce time taken for initial snapshot restore for postgres plugin. Avoid duplicate writes of accounts at startup. Doing account plugin notification and indexing in parallel.
Improved error handling for postgres plugin to show the real db issues for debug purpose
Added more metrics for postgres plugin.
Refactored plugin centric code out to a sub module from accounts_db and added unit tests
