feat: Extend new search for project/tables as well.

[kazoompa]

Currently the search is implemented primarily for variables but it could be bemeficial to extend it for searching other entities such as datasources and tables.

Two possible use-cases:

1. When searching for tables by EntityType Opal returns all matching tables to the client code which can be very expensive when there are a large number of tables. This can be improved greatly if client code could filter the tables by name, entity type or other useful attributes and return the matching result set.
2. In the project listing page, once the search is augmented, users can filter the list by indexed attributes of datasources/projects, tables or variables.

The latter use-case may alter the way the projects listing page is currently implemented in that, we no longer get the digests but a paginated filtered list... to be decided.