Clickhouse: check if existing tables have compatible schema

[Amogh-Bharadwaj]

During SetupFlow and ValidateMirror in PG to Clickhouse CDC, if a target table exists already, check if the columns have compatible data types. Essentially we should be able to insert rows into the table based on source schema target schema data type mapping. Deviations like Nullable(type) instead of type and uint64 instead of int64 should be tolerated