[RRFaM] When writing FaM images to txn table, write oplog entries with `needsRetryImage`

• Add optional `needsRetryImage` field to oplog entry idl
  • It takes on string enum values of `preImage` and `postImage`
• When writing oplog entries with retryableFaMStorageLocation=transactionsTable, set this field on oplog entries.

Nothing will yet be reading this value.