bug 8252: (follow-up) test both GRS1 and DOM indexing

bug 8252: (follow-up) test both GRS1 and DOM indexing

This patch expands t/db_dependent/Search.t to run
the same tests using both the GRS-1 and DOM indexing
modes.  It also adds hooks in zebra_config.pl to make
it easier to stage test cases for non-MARC21 Zebra
indexing.

Note that in DOM mode one of the tests is currently a
TODO, as relevance ranking for wegihted queries differs
between GRS-1 and DOM.

To test:

[1] Verify that prove -v t/db_dependent/Search.t passes.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>