Add PATCH schemas to arm-common-types

[markcowl]

A few common-types schemas will not work in PATCH bodies, due to having required properties or using the wrong visibility.

• Ensure that PATCH schemas are generated for necessary arm-common-types types as part of common-types swagger generation
• Ensure that PATCH requests use the new common-types schemas

This should be required for:

ManagedServiceIdentity
SystemAssignedServiceIdentity
Plan
Sku
TrackedResource