Make metadata that combines flags and access privileges more compact

[andy31415]

https://github.com/project-chip/connectedhomeip/blob/master/src/app/data-model-provider/MetadataTypes.h defines several classes that combine some BitFlags (which are generally not as many) and access privileges.

Since these structures will be stored in structs, making the structures smaller will result in resource saving. We would want storage to be combined to use 3 bits for access privileges (available list at https://github.com/project-chip/connectedhomeip/blob/master/src/access/Privilege.h) and the rest for actual flags.

As an external interface, we should have getter-style operations like Access::Privilege GetInvokePrivilege() and BitFlags<CommandQualityFlags> GetQualities() as examples and the actual storage of things should be internal implementation details.

Structures to change:

• AcceptedCommandEntry
• AttributeEntry