refactor: move open class methods from extension to class

[cbaker6]

New Pull Request Checklist

• [x] I am not disclosing a vulnerability.
• [x] I am creating this PR in reference to an issue.

Issue Description

The compiler doesn't like for Swift based open methods to be declared in extensions. More info here. When a method is open in Xcode 14, a warning is thrown by the compiler.

Related issue: #n/a

Approach

Move open methods inside their respective classes.

TODOs before merging

• [x] Ensure all tests still pass

[parse-github-assistant[bot]]

Thanks for opening this pull request!

• 🎉 We are excited about your hands-on contribution!

[codecov[bot]]

Codecov Report

Merging #389 (3e73598) into main (413e995) will decrease coverage by 0.02%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #389      +/-   ##
==========================================
- Coverage   89.68%   89.66%   -0.03%     
==========================================
  Files         155      155              
  Lines       14121    14125       +4     
==========================================
  Hits        12665    12665              
- Misses       1456     1460       +4     

Impacted Files	Coverage Δ
Sources/ParseSwift/LiveQuery/Subscription.swift	97.87% <ø> (ø)
...es/ParseSwift/LiveQuery/SubscriptionCallback.swift	70.45% <ø> (ø)
Sources/ParseSwift/Objects/ParseInstallation.swift	85.46% <100.00%> (+0.06%)	:arrow_up:
Sources/ParseSwift/LiveQuery/ParseLiveQuery.swift	76.16% <0.00%> (-0.59%)	:arrow_down:

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