Index required wallet connect DB columns before enabling the feature

[stefandunca]

As reported by @cammellos the following columns (and any used in the meantime) should be indexed

• wallet_connect_sessions

  • disconnected, expiry, test_chains (WHERE clause)
  • optionally: pairing_topic
  • already indexed: topic

• wallet_connect_dapps

  • url is primary key

• Run explain query plan .... for all the queries we do and ensure the index is used

• Optionally implement basic benchmarks for the usual operations "list dapps", "disable a session", "disable all sessions for pairing topic" ...