Bug 37120: Add heading subfields for 647 (MARC21)

This patch updates the default MARC21 bibliographic framework to add missing
subfields to field 647.

To test:
1. Apply patch and reset_all
2. Go to Administration > MARC bibliographic framework
3. Click Actions next to the default framework and choose MARC structure
4. Search for field 647
5. Click Actions > View subfields (or Edit subfields)
6. Check that subfields match the documentation
   https://www.loc.gov/marc/bibliographic/bd647.html
   (note that subfields $4 and $e are added in bug 37114)

Added subfields are:
- a - Named event (NR)
- c - Location of named event (R)
- d - Date of named event (NR)
- g - Miscellaneous information (R)

7. Optional: run the framework test in Administration > MARC bibliographic
   framework test
   --> All should be OK

Signed-off-by: Phil Ringnalda <phil@chetcolibrary.org>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>

installer/data/mysql/en/marcflavour/marc21/mandatory/marc21_framework_DEFAULT.yml

@@ -37234,6 +37234,78 @@ tables:
           link: ""
           defaultvalue:
 
+        - tagfield: "647"
+          tagsubfield: "a"
+          liblibrarian: "Named event"
+          libopac: "Named event"
+          repeatable: 0
+          mandatory: 0
+          kohafield: ""
+          tab: 6
+          authorised_value: ""
+          authtypecode: ""
+          value_builder: ""
+          isurl:
+          hidden: -6
+          frameworkcode: ""
+          seealso: ""
+          link: ""
+          defaultvalue:
+
+        - tagfield: "647"
+          tagsubfield: "c"
+          liblibrarian: "Location of named event"
+          libopac: "Location of named event"
+          repeatable: 1
+          mandatory: 0
+          kohafield: ""
+          tab: 6
+          authorised_value: ""
+          authtypecode: ""
+          value_builder: ""
+          isurl:
+          hidden: -6
+          frameworkcode: ""
+          seealso: ""
+          link: ""
+          defaultvalue:
+
+        - tagfield: "647"
+          tagsubfield: "d"
+          liblibrarian: "Date of named event"
+          libopac: "Date of named event"
+          repeatable: 0
+          mandatory: 0
+          kohafield: ""
+          tab: 6
+          authorised_value: ""
+          authtypecode: ""
+          value_builder: ""
+          isurl:
+          hidden: -6
+          frameworkcode: ""
+          seealso: ""
+          link: ""
+          defaultvalue:
+
+        - tagfield: "647"
+          tagsubfield: "g"
+          liblibrarian: "Miscellaneous information"
+          libopac: "Miscellaneous information"
+          repeatable: 1
+          mandatory: 0
+          kohafield: ""
+          tab: 6
+          authorised_value: ""
+          authtypecode: ""
+          value_builder: ""
+          isurl:
+          hidden: -6
+          frameworkcode: ""
+          seealso: ""
+          link: ""
+          defaultvalue:
+
         - tagfield: "647"
           tagsubfield: "v"
           liblibrarian: "Form subdivision"