[SPARK-3131][SQL] Allow user to set parquet compression codec for writing ParquetFile in SQLContext

There are 4 different compression codec available for ```ParquetOutputFormat```

in Spark SQL, it was set as a hard-coded value in ```ParquetRelation.defaultCompression```

original discuss:
https://github.com/apache/spark/pull/195#discussion-diff-11002083

i added a new config property in SQLConf to allow user to change this compression codec, and i used similar short names syntax as described in SPARK-2953 #1873 (https://github.com/apache/spark/pull/1873/files#diff-0)


btw, which codec should we use as default? it was set to GZIP (https://github.com/apache/spark/pull/195/files#diff-4), but i think maybe we should change this to SNAPPY, since SNAPPY is already the default codec for shuffling in spark-core (SPARK-2469, #1415), and parquet-mr supports Snappy codec natively (https://github.com/Parquet/parquet-mr/commit/e440108de57199c12d66801ca93804086e7f7632).

I think making this snappy as you proposed is reasonable.