add Waiter for checking if table is ready

[tarzanek]

Target table not ready yet. Waiting 1 second.

in https://github.com/scylladb/scylla-migrator/pull/141/files/e7e7f4eff9999f35cebb047789537e1df65421a0#diff-11993c65c362dc321c50c2c397371e56ad8174905095754dfc8c979fbf7342d6

as per @julienrf If we upgrade the AWS SDK to the v2 we can use the new Waiter abstraction.

[tarzanek]

ref https://github.com/scylladb/scylla-migrator/pull/141

[tarzanek]

dtto in same file re while for

 s"Stream not yet enabled (status ${streamStatus}); waiting for 5 seconds and retrying")
        Thread.sleep(5000)