LP#1745207: tie together copy_tag() and site() search filters

LP#1745207: tie together copy_tag() and site() search filters

The copy_tag() filter will now restrict itself to records that
have copies that both have matching copy tags and a circ_lib
within the site() scope.

To test
-------
[1] Define two digital bookplate copy tags at two difference org units, e.g.,
    "BR1 Smith" at BR1 and "BR4 Smith" at "BR4".
[2] Arrange that a record has items in both BR1 and BR4, and assign the "BR4 Smith"
    copy tag to one of the BR4 items.
[3] On a separate record, set up a similar situation, but use BR1 instead.
[4] Enable the digital bookplate search option and do a bookplate search
    for "Smith" with the scope limited to BR1.
[5] Note that both of the records set up in #2 and #3 are included in the results
    set.
[6] Apply the patch and repeat step 5. This time, only the record set up in #3
    should be included.

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>
Signed-off-by: Garry Collum <gcollum@gmail.com>