[enhancement] Fully flesh out the Digital Twin Graph's member path concept

[ashbeitz]

Description

The member path concept allows a request to scope its target, when necessary, to a part of an instance, rather than just the entire instance. It is used in the Digital Twin Graph's Get, Set and Invoke operations. In the samples that currently exist, it is used to specify the instance's operation to perform. The samples do not yet demonstrate how it can be used by the Get and Set operations. We should add these samples.

Acceptance criteria

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