Limit number of fields to be allowed to 64 as Enterprise search < 7.7 has a limitation of 64 fields

Issue Summary:

Enterprise App Search below 7.7 allows only 64 fields in the schema. This check needs to be added in the Schema form as well. Please refer to Elastic App Search Documentation for the limits

Issue Resolution

Add a js behavior to check the number of fields and show a warning message "Enterprise App search allows a maximum of 64 schema fields to be added Please refer to the Elastic App Search Documentation"once user selects 64 fields and disable Submit button when user crosses 64 fields.