Improve error output after a failed FK constraint check

[peterjan]

If PRAGMA foreign_key_check fails after running a migration, renterd currently outputs totally useless information. I updated the code to scan for all errors and indicate what FK failed on what table on what row.

Before:

failed to create node: failed to perform migrations: migration X failed: transaction failed (attempt 1): foreign key constraints are not satisfied, err sql: expected 4 destination arguments in Scan, not 0

After:

failed to create node: failed to perform migrations: migration X failed: transaction failed (attempt 1): foreign key constraint violation in table 'slabs': row 2423432, foreign key buffered_slabs