Ways to improve relayer sync on startup

[r0wdy1]

1. Create a regular job to backup the relayer's database files for

• transactions
• state roots
• nullifiers

The job copies all the files to a newly created folder in a specified path. Only N last backups are needed, so the oldest one is deleted whenever there is already N backups stored.

2. The relayer startup code must be modified so that external backup files could be used as a starting point. The path must be passed as an argument

[ulyanas]

1. First step would be to test reorgs and similar cases - @r0wdy1