Bug 36952: Add 370 to authority index (MARC21)

Bug 36952: Add 370 to authority index (MARC21)

This enhancement adds field 370 to MARC21 default authority
index mappings.

To test:
1. Import the attached .mrc file
2. Go to Authorities
3. Search 'Main heading' for quebec
   --> 1 result (normal)
4. Search 'Entire record' for quebec
   --> 1 result
5. Go to the OPAC > Authority search
6. Redo steps 3 and 4
   --> Same results
7. Apply patch
8. Reindex authorities (in KTD shell:
   koha-elasticsearch --rebuild -a -v -r kohadev)
9. Redo step 3
   --> Still 1 result (normal)
10. Redo step 4
    --> 2 results
11. Redo step 5-6
    --> Same results as steps 9-10

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>