What does this implement/fix? Explain your changes.

Implements __delitem__ for IList<T> and IDictionary<K,V>

Fixes memory leak on using indexer setter.

Fixes crash on attempting to do del o[...] on .NET objects apart from arrays.

Does this close any currently open issues?

Fixes #2530

Checklist

Check all those that are applicable and complete.

• Make sure to include one or more tests for your change
• If an enhancement PR, please create docs and at best an example
• Ensure you have signed the .NET Foundation CLA
• Add yourself to AUTHORS
• Updated the CHANGELOG