fix: prevent dangling references in dict and listCallbackProperties

[iisakkirotko]

Description

While implementing viewer closing in glue-jupyter, I found that ListCallbackProperty and DictCallbackProperty would often have a dangling references to instances of objects that use them. Using a weakref in referencing those objects will let them be garbage collected.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.78%. Comparing base (8f8eb9a) to head (f2cadaf).
Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #43   +/-   ##
=======================================
  Coverage   96.77%   96.78%           
=======================================
  Files          18       18           
  Lines        2356     2361    +5     
=======================================
+ Hits         2280     2285    +5     
  Misses         76       76           

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[dhomeier]

Thanks, implementation looks good, though I am not deeply familiar with the use case.

1. Please rebase this as well to get the linux-ci tests.
2. Could a test be added to test_containers.py to check the type the callback uses, or maybe even that garbage collection works?

[astrofrog]

I've rebased, and CI is passing. Adding tests for this kind of issue is not trivial, we try and do this in glue by counting objects with objgraph, but it's a bit messy and sometimes flaky as it depends on the garbage collection. Since all the current tests pass, I think we should merge this, and consider potentially adding tests for the weakref stuff here and elsewhere in echo in future if we encounter bugs related to this.