Ignore computing writetime (& TTLs) for tables without non-primary key columns

[msmygit]

Ignore computing writetimes (& TTLs) when there are no writetime capable columns in the given table schema.

Currently we hit this error which stems from this condition,

24/02/05 15:32:07 ERROR WritetimeTTL: WriteTimestamp filter is configured but no WriteTimestamp columns are de
fined
24/02/05 15:32:07 INFO WritetimeTTL: Feature WritetimeTTL is disabled
24/02/05 15:32:07 ERROR CopyJobSession: Feature com.datastax.cdm.feature.WritetimeTTL is not valid.  Please ch
eck the configuration.
24/02/05 15:32:07 INFO WritetimeTTL: PARAM -- spark.cdm.filter.java.writetime.min: 1668470400000 datetime is 1
970-01-20T07:27:50.400Z 
24/02/05 15:32:07 INFO WritetimeTTL: PARAM -- spark.cdm.filter.java.writetime.max: 2699474926455700 datetime i
s 2055-07-17T22:08:46.455Z