Deepcopy Collection properties on clone

[sunu]

Related Issue(s): Fixes #787

Description: Makes sure that all the mutable properties of a Collection get deepcopied when the collection is cloned. Implements clone on Summaries to make sure cloned collection will point to a new instance of Summaries after being cloned.

I have some weird mypy errors from the tests that I added. Still trying to figure out how to fix. I would love some help on that.

PR Checklist:

• Code is formatted (run pre-commit run --all-files)
• Tests pass (run scripts/test)
• [NA] Documentation has been updated to reflect changes, if applicable
• This PR maintains or improves overall codebase code coverage.
• Changes are added to the CHANGELOG. See the docs for information about adding to the changelog.

[codecov-commenter]

Codecov Report

Merging #794 (5bd15cf) into main (a6c8927) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #794      +/-   ##
==========================================
+ Coverage   94.57%   94.59%   +0.01%     
==========================================
  Files          79       79              
  Lines       11660    11690      +30     
  Branches     1372     1372              
==========================================
+ Hits        11028    11058      +30     
  Misses        453      453              
  Partials      179      179              

Impacted Files	Coverage Δ
pystac/catalog.py	92.15% <ø> (ø)
pystac/collection.py	94.26% <ø> (ø)
pystac/summaries.py	78.88% <100.00%> (+0.98%)	⬆️
tests/extensions/test_scientific.py	100.00% <100.00%> (ø)
tests/test_collection.py	100.00% <100.00%> (ø)
tests/test_summaries.py	100.00% <100.00%> (ø)

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[sunu]

Mypy errors should be fixed now. I've also added a changelog entry.

[sunu]

Rebased the branch on main to make sure the ci uses Python 3.11.0-alpha.7. Hopefully that'll fix the failing tests on 3.11

[sunu]

Hi @duckontheweb, @gadomski! now that all the tests are passing, I'd love to get some review 🙂

[duckontheweb]

Thanks for this @sunu. I had one comment on whether we really need to deepcopy the stac_extensions property. Other than that it looks good to me.

[duckontheweb]

Thanks again for the contribution @sunu !