Run tests of libpq on installcheck-world, checkprep and check-world

The regression tests of libpq have been converted to a TAP test as of
ac25173, but they were not run when running the global make targets
mentioned in $subject as the code only considered src/interfaces/ecpg/
as a path to run.  This switches to src/interfaces/, to always include
the tests of libpq in each run.

Reported-by: Justin Pryzby
Reviewed-by: Andres Freund
Discussion: https://postgr.es/m/20220529151850.GN19626@telsasoft.com

Author: michaelpq

GNUmakefile.in

@@ -68,10 +68,10 @@ check check-tests installcheck installcheck-parallel installcheck-tests: CHECKPR
 check check-tests installcheck installcheck-parallel installcheck-tests: submake-generated-headers
 	$(MAKE) -C src/test/regress $@
 
-$(call recurse,check-world,src/test src/pl src/interfaces/ecpg contrib src/bin,check)
-$(call recurse,checkprep,  src/test src/pl src/interfaces/ecpg contrib src/bin)
+$(call recurse,check-world,src/test src/pl src/interfaces contrib src/bin,check)
+$(call recurse,checkprep,  src/test src/pl src/interfaces contrib src/bin)
 
-$(call recurse,installcheck-world,src/test src/pl src/interfaces/ecpg contrib src/bin,installcheck)
+$(call recurse,installcheck-world,src/test src/pl src/interfaces contrib src/bin,installcheck)
 $(call recurse,install-tests,src/test/regress,install-tests)
 
 GNUmakefile: GNUmakefile.in $(top_builddir)/config.status