Refactor swagger definitions to factor out reusable components

[dsbivan]

Description
As part of the OAS 3 migration, all reusable components were inlined into the various objects that use them.

This includes:

• responses
• parameters
• headers

A tightening up of the schema definitions will make it easier to read and may help code generators

Related Work Items
Those swagger definitions which went through the OAS3 migration

- cds_admin
- cds_banking
- cds_common
- cds_dcr
- cds_register

[nils-work]

Repetitive (common) headers in the Banking spec., like x-v could reference a single structure in components.parameters, like RequestHeader_x-v