Enhance `zowex compress` error message for PDSE/Library

[zFernand0]

Describe the bug

Some operations may not recognize that a PDS is in fact a PDS.
The issue is when we gather fldata of a //'HLQ.PDS.DNSTYPE.LIBRARY'

To Reproduce

zowex ds create HLQ.PDS.DNSTYPE.LIBRARY --dsorg PO --dirblk 2 --dsntype LIBRARY
zowex ds compress HLQ.PDS.DNSTYPE.LIBRARY
Error: data set 'HLQ.PDS.DNSTYPE.LIBRARY' is not a PDS

Expected and actual results

Expected to be able to compress the data set

Describe your environment

Additional context

[zFernand0]

ISPF may show the following messages:

Compress not allowed
The specified library is a PDSE and cannot be compressed.

Unsupported function
The requested function is not supported for PDSE datasets.