## Motivation
CSV data source was contributed by Databricks. It is the inlined version of https://github.com/databricks/spark-csv. The data source name was `com.databricks.spark.csv`. As a result there are many tables created on older versions of spark with that name as the source. For backwards compatibility we should keep the old name.

## Proposed changes
`com.databricks.spark.csv` was added to list of `backwardCompatibilityMap` in `ResolvedDataSource.scala`

## Tests
A unit test was added to `CSVSuite` to parse a csv file using the old name.

Author: Hossein <hossein@databricks.com>

Closes #11589 from falaki/SPARK-13754.