Restore Schema API GET method functionality removed by SOLR-8736

The following schema API GET functionality was removed under SOLR-8736; some of this functionality should be restored:

• schema/copyfields:
  • The following information is no longer output:
    • destDynamicBase: the matching dynamic field pattern for the destination
    • sourceDynamicBase: the matching dynamic field pattern for the source
  • The following request parameters are no longer supported:
    • dest.fl: include only copyFields that have one of these as a destination
    • source.fl: include only copyFields that have one of these as a source
• schema/dynamicfields:
  • The following request parameters are no longer supported:
    • fl: a comma and/or space separated list of dynamic field patterns to include
• schema/fields and schema/fields/fieldname:
  • The following information is no longer output:
    • dynamicBase: the matching dynamic field pattern, if the includeDynamic param is given (see below)
  • The following request parameters are no longer supported:
    • fl: (only supported without /fieldname): a comma and/or space separated list of fields to include
    • includeDynamic: output the matching dynamic field pattern as dynamicBase, if fieldname, or field(s) listed in fl param, are not explicitly declared in the schema
• schema/fieldtypes and schema/fieldtypes/typename:
  • The following information is no longer output:
    • fields: the fields with the given field type
    • dynamicFields: the dynamic fields with the given field type