Re-enable dbi backend basic tests with g_tester

Combining business and basic into renamed test-backend-dbi-basic--
not utest because these are integration tests rather than unit tests.
Remove all of the no-longer-used test program files.

The actual test routines remain in test-dbi-stuff.c and test-dbi-business.c
just to keep the size of test-backend-dbi-basic.c reasonable.

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23169 57a11ea4-9604-0410-9ed3-97b8803252fd