This patch moves all the indexing, event storing and searching into a
separate class.
The index and message store are now represented as a single class and
messages are indexed and stored atomically now which should minimize the
chance of store/index inconsistencies.
Messages are now loaded from the store as a single SQL query and the
context for the messages is as well loaded from the store instead of
fetched from the server.
The room state and start/end tokens for the context aren't currently
loaded.
This patch adds support for the Matrix search API endpoint.
Events are stored in the pan sqlite database while the indexing is
handled by tanvity.
An tantivy index is created for each pan user. Currently only ordering
by ranking is supported, and all the search options are ignored for now.
