[Update] Sample type and member access levels

[CalebRas]

Description

This PR updates the access levels of types and members used by samples to make them more encapsulated. This was done to:

• Prevent types and members being reused in other samples. (Samples should be stand alone to allow users to copy and paste them, see related comment.)
• Prevent existing declarations interfering with new ones. (E.g., the internal Model used by Edit geodatabase with transactions was preventing any new samples from implementing their own file-private Model.)

Overview of changes (corresponding to a commit):

• Make types file-private or nested (or both).
• Make extensions private were possible.
• Make sample view members (properties, methods, & nested types) private were possible.

Linked Issue(s)

Closes #375.

How To Test

There are no functionality changes in this PR so ensuring the project builds should be sufficient.