Update pan/orbit state icon

[mmisol]

Purpose

Fixes issues related to the state of the pan icon not reflecting the
actual current state.

There were two problems preventing this from updating.

Some actions did not seem to trigger a property change on IsPlanning
and IsOrbiting at the BackgroundPreviewViewModel. There are properties
with the same name in the local view model that get updated more
consistently.

Some actions were triggering property change events in the wrong place.
These were moved to the right place.

While there were no reported issues with IsOrbiting, this property
should behave in the same way, so the same changes were applied.

Declarations

Check these if you believe they are true

• The codebase is in a better state after this PR
• Is documented according to the standards
• The level of testing this PR includes is appropriate
• User facing strings, if any, are extracted into *.resx files
• All tests pass using the self-service CI.
• Snapshot of UI changes, if any.
• Changes to the API follow Semantic Versioning and are documented in the API Changes document.
• This PR modifies some build requirements and the readme is updated

Reviewers

@QilongTang @zeusongit

FYIs

@DynamoDS/dynamo

[zeusongit]

Looks good, but maybe add some comments for some context like the once you removed in Escape() and ToggleOrbit().

[mmisol]

@zeusongit I didn't actually remove those comments. Just moved them to the RefreshState() function which is now called from those other places.

[zeusongit]

Ah.. ok, got it.