Further refinement of the canal protocol

Feature Request

Is your feature request related to a problem? Please describe:

The current canal protocol implementation only supports the replication of row-level changelogs. We would like to support a more complete canal protocol to improve its universality.

Describe the feature you'd like:

• Support more field in canal protocol (such as Column.mysqlType)
• Support transaction in canal protocol (TransactionBegin and TransactionEnd message), only need to support single table transaction now.
• Add a canal demo consumer, used in the integration test to verify the protocol works as expected.

Teachability, Documentation, Adoption, Migration Strategy:

Canal proto: https://github.com/pingcap/ticdc/tree/master/proto