Add TAP test in pg_dump with --format=tar and --compress

Add TAP test in pg_dump with --format=tar and --compress

This combination of options has never been supported, and it has never
been checked in the regression tests.  When building the code without
zlib support, pg_dump is allowed to run and it generates a warning to
inform that any contents are dumped as uncompressed.  The tests added by
this commit check both behaviors.

Author: Georgios Kokolatos, Rachel Heaton
Discussion: https://postgr.es/m/faUNEOpts9vunEaLnmxmG-DldLSg_ql137OC3JYDmgrOMHm1RvvWY2IdBkv_CRxm5spCCb_OmKNk2T03TMm0fBEWveFF9wA1WizPuAgB7Ss=@protonmail.com