## What changes were proposed in this pull request?

Allowing truncate to a specific number of character is convenient at times, especially while operating from the REPL. Sometimes those last few characters make all the difference, and showing everything brings in whole lot of noise.

## How was this patch tested?
Existing tests. + 1 new test in DataFrameSuite.

For SparkR and pyspark, existing tests and manual testing.

Author: Prashant Sharma <prashsh1@in.ibm.com>
Author: Prashant Sharma <prashant@apache.org>

Closes #13839 from ScrapCodes/add_truncateTo_DF.show.