NodeModel dispose on workspace close

[bendikberg]

Purpose

When a workspace is closed, a majority of the time is spent by nodes reacting to connector deletions. By unsubscribing from connector events before the a workspace closes, the time to get back to the main menu goes down substantially.

For the MaRS graph, this takes workspace close from about 8 to 4 seconds. For the Car_Configurator graph, this takes workspace close from about 2 minutes down to 40 seconds.

Performance

Old

New

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
• This PR contains no files larger than 50 MB

Release Notes

N/A

Reviewers

@mjkkirschner

FYIs

@dimven