fix(#7456): allow children of Overlay Plots to be removed

[ozyx]

Closes #7456

Describe your changes:

The StalenessMixin assumes that it will always be passed a domainObject when looking to unsubscribe from staleness. However, in the case of Overlay Plots, it receives an Identifier directly, causing an error. This modifies that logic to check if its an Identifier first before attempting to extract an Identifier from the object.

• Refactors objectUtils to have ESM exports of individual helper functions
• Refactors usage of objectUtils helper functions to use ESM imports
• Refactors some Vue anti patterns out of PlotElementsPool.vue

All Submissions:

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Is this change backwards compatible? For example, developers won't need to change how they are calling the API or how they've extended core plugins such as Tables or Plots.

Author Checklist

• Changes address original issue?
• Tests included and/or updated with changes?
• Has this been smoke tested?
• Have you associated this PR with a type: label? Note: this is not necessarily the same as the original issue.
• Have you associated a milestone with this PR? Note: leave blank if unsure.
• Is this a breaking change to be called out in the release notes?
• Testing instructions included in associated issue OR is this a dependency/testcase change?

Reviewer Checklist

• Changes appear to address issue?
• Reviewer has tested changes by following the provided instructions?
• Changes appear not to be breaking changes?
• Appropriate automated tests included?
• Code style and in-line documentation are appropriate?

[codecov]

Codecov Report

Attention: 15 lines in your changes are missing coverage. Please review.

Comparison is base (6393a77) 55.36% compared to head (367bbee) 55.13%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7516      +/-   ##
==========================================
- Coverage   55.36%   55.13%   -0.24%     
==========================================
  Files         671      672       +1     
  Lines       27013    27026      +13     
  Branches     2633     2634       +1     
==========================================
- Hits        14957    14900      -57     
- Misses      11332    11400      +68     
- Partials      724      726       +2     

Flag	Coverage Δ
e2e-full	21.69% <40.29%> (-19.41%)	⬇️
e2e-stable	59.51% <59.70%> (+0.13%)	⬆️
unit	48.44% <76.31%> (-0.01%)	⬇️

Files	Coverage Δ
src/api/composition/CompositionProvider.js	74.35% <100.00%> (ø)
src/api/composition/DefaultCompositionProvider.js	95.45% <100.00%> (ø)
src/api/objects/MutableDomainObject.js	100.00% <100.00%> (ø)
src/api/objects/RootRegistry.js	85.71% <100.00%> (ø)
src/api/objects/object-utils.js	97.36% <ø> (ø)
src/api/telemetry/TelemetryAPI.js	89.21% <100.00%> (ø)
...ugins/importFromJSONAction/ImportFromJSONAction.js	65.26% <100.00%> (ø)
...rc/plugins/inspectorViews/elements/ElementItem.vue	0.00% <ø> (ø)
src/plugins/notebook/utils/notebook-storage.js	85.45% <ø> (ø)
...rc/plugins/staticRootPlugin/StaticModelProvider.js	98.36% <100.00%> (ø)
... and 11 more

... and 8 files with indirect coverage changes

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[unlikelyzero]

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