Purpose

Before these changes running just DynamoCoreWPFTests.dll consumed 6GB of ram on my machine.
After these changes memory use is approximately 1GB and forcing a garbage collection brings it down to 300~ megs.

There are likely a bunch of extraneous changes here and also - these changes are just WIP - they need to be cleaned up.

But here are some notes on what I found:

• NodeViews leak, completely, every single customized node view was not being GC'd - these hold all sorts of things and some of them even have references to DynamoView/DynamoModel so then EVERYTHING leaks as a consequence.
• DynamoView.Dispose was never called - as a consequence:

• ViewExtensions never had their Dispose method called, only their shutdown method ... I removed the dispose code because some extensions already called this from shutdown and theres some caught exceptions being thrown - this is a TODO

• many retention paths were holding onto the underlying canvases in Helix.

• WorkspaceView and DynamoView left a bunch of handlers dangling.

• Static references under some circumstances do not get GC'd as they live in a global object the CLR builds, these might not get cleaned up during tests so I've set them null during cleanup. Need to check if these are required.

• I noticed some very strange behavior with readonly fields not being cleaned up - research seems split on if these can be a problem, need to check if this can be reverted.

• Because of the design of ViewLoadedParams passed to ViewExtensions it's difficult to cleanup the handlers that are created there, I ended up storing a reference to a single params and using it for all view extensions that are loaded at Dynamo startup - I think this is okay. - though likely we could solve this more elegantly - it also means that view extensions loaded after startup, still leak, but thats an edge case.

• InforBubble (error view) leaks - made some improvments.

• removed Suppress GC on Defaultwatch3dViewModel - need to check if this was required - I don't see why we would want this though - we don't implement a finalizer.

• removed a bunch of anonymous event handlers which caused leaks, while these are great and make code more succinct and readable, I think we should disallow their use unless the author memory profiles them or has a convincing argument why they will not introduce a leak... usually they are fine if they do not reference any external objects, IE an event on the same object on which the handler is defined.

• CustomNodeWorkspaceModels leak - these were never cleaned up because we only clean the workspaces in the DynamoModel.Workspaces collection - but custom node workspaces are not in that collection unless they are actually open in a tab. When the customNodeManager is cleaned up now, these are uninitialized by the CNM which cleans them up.

• Added additional dispose steps to HelixWatch3dViewModel as it did not call the base class dispose, and it did not clear all collections - not sure if this is required, but calling the base class is.

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.