Rename example_plugins to example_apps

[glennmatthews]

What's Changed

Happy Friday afternoon! As part of the ongoing shift in nomenclature from Nautobot "plugins" to Nautobot "Apps", this PR's primary goal is to migrate example_plugin and example_plugin_with_view_override to example_app and example_app_with_view_override respectively, including their usage in Nautobot's test automation and documentation.

The secondary goal was to replace all other references to "plugins" in the examples/ directory with "App" references, except in cases where doing so would require impactful code changes in core (e.g. settings.PLUGINS, plugins: and plugins-api: URL namespaces, etc.)

A tertiary goal was to, in core files that were already being touched as part of the above, make a first stab at cleaning up docstrings, comments, and the like to also use the newer nomenclature, but this is best-effort only at this time and will require more exhaustive work in a future PR.

Screenshots

TODO

• Explanation of Change(s)
• Added change log fragment(s) (for more information see the documentation)
• Attached Screenshots, Payload Example
• Unit, Integration Tests
• Documentation Updates (when adding/changing features)
• Example Plugin App Updates (when adding/changing features)
• Outline Remaining Work, Constraints from Design