INT-3339: Add `priority` to the `JdbcChannelMS`

JIRA: https://jira.spring.io/browse/INT-3339

INT-3339: Improve `priority` logic

INT-3339: Add `MESSAGE_SEQUENCE` stuff

INT-3339: Docs

INT-3339: Polishing and PR comments

INT-3339 Polishing

Fix Oracle Test Case.
Doc polishing.