[SPARK-3205] add EscapedTextInputFormat

Text records may contain in-record delimiter or newline characters. In such cases, we can either encode them or escape them. The latter is simpler and used by Redshift's UNLOAD with the ESCAPE option. The problem is that a record will span multiple lines. We need an input format for it.

@marmbrus
BTW if you do add a new package you'll have to fix the SBT code that generates Javadocs and Scaladocs to make sure it appears in the right ones.