* Modified DrawValue method of BaseVariableDrawer to be virtual.
* Modified BaseReferenceDrawer to check if constant property height is greater than a single line, and if it is to display it inline below the field rather than to the right of the label. For existing value type reference types this will not change their UX, but for more complex types it allows for more space to be displayed across the entire width of the inspector. Popup will display as normal.

* Created SceneVariable as a generic BaseVariable of type SceneInfo, where SceneInfo contains serializable information about a scene asset.
* Created SceneVariableEditor to allow for custom inspection of SceneVariable as well as SceneInfoPropertyDrawer for the serializable value type. This allows for a user to assign a SceneAsset to an object field and ping it while only the serialized relevant values (full path, index and enabled status in build settings) are persisted in the ScriptableObject. Helpful warnings are shown for the user if a scene is not assigned, present in the build settings, or enabled in the build settings.
* Created SceneCollection
* Created AssemblyInfo.cs as a code file for assembly attributes for the ScriptableObject-Architecture Assembly Definition. The current assembly attribute allows for the internals of this assembly to be visible to ScriptableObject-Architecture.Editor. This allows for internal types and members to be used in inspectors, editor windows without directly exposing them to end-users.

* Modified GetPropertyHeight in BaseReferenceDrawer to only use the inline height calculation if the constant value property height would be greater than a single line.
* Modified the width of the popup style button to be a constant fixed width of 25f. This style seems to have an issue when shown in a list that its normal fixed width is obscuring the clickable element and buffing this width to a fixed size makes this area clickable again.

* This is content added to make it easier to test this PR in the editor, it can be discarded after reviewing