Set application_name per-test in isolation and ecpg tests.

Tom Lane <tgl@sss.pgh.pa.us>

Commit: b1907d6882205319822c7452ce6b5e71ee2867be
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: 2019-08-27T23:49:09Z
Releases: 13.0
Set application_name per-test in isolation and ecpg tests.

Commit a4327296d taught pg_regress proper to do this, but
missed the opportunity to do likewise in the isolationtester
and ecpg variants of pg_regress.  Seems like this might be
helpful for tracking down issues exposed by those tests.

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