[server] Add delay before setuping database and running migrations

Summary:
Linear: https://linear.app/comm/issue/ENG-1350/investigate-why-new-messages-are-not-displayed-when-keyserver
Introduce 5s delay before running database setup script and migrations in dev mode.
This prevents executing migrations and db setup script while project files are compiled after running yarn dev and nodemon restarts a few times.

Test Plan: I dropped database, and run yarn dev with and without fix, confirming that DB setup was fully completed using logs. Also checked threads table in DB to confirm the initial threads are created.

Reviewers: palys-swm, atul, ashoat

Reviewed By: ashoat

Subscribers: ashoat, Adrian, yayabosh

Differential Revision: https://phab.comm.dev/D4506