Retry cleanup PK conversion for events table

What does this MR do and why?

Retry cleanup PK conversion for events table

At the first attempt, migration was blocked by an autovacuum process, which prevented the table to acquiring an exclusive lock, resulting in a timeout.

• Check incident issue
• Check incident slack thread

Simon Tomlinson: There was a wraparound-prevention autovacuum of events during this incident, which caused the lock queueing that led to this migration failing. If we avoid a time window with a wraparound-prevention vacuum, we should be able to simply run the same code in a new migration. Link

db:check-migrations jobs are expected to fail

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #414777 (closed).