refactor: Make some ParseObject methods required

[cbaker6]

New Pull Request Checklist

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

Issue Description

Certain methods like: init(objectId: String), hasSameObjectId(), toPointer(), endpoint(), and isSaved() are not required in the ParseObject protocol, preventing the SDK from taking advantage of developer implementations.

Approach

Add the aforementioned methods as required and preserve their default implementations.

TODOs before merging

• Add entry to changelog
• Add changes to documentation (guides, repository pages, in-code descriptions)

[codecov]

Codecov Report

Merging #96 (36cfaa2) into main (a746db0) will decrease coverage by 0.01%.
The diff coverage is 94.28%.

@@            Coverage Diff             @@
##             main      #96      +/-   ##
==========================================
- Coverage   91.46%   91.46%   -0.01%     
==========================================
  Files         172      172              
  Lines       15295    15240      -55     
==========================================
- Hits        13990    13939      -51     
+ Misses       1305     1301       -4     

Impacted Files	Coverage Δ
...urces/ParseSwift/API/API+NonParseBodyCommand.swift	80.00% <ø> (ø)
Sources/ParseSwift/API/API.swift	99.41% <ø> (ø)
Sources/ParseSwift/API/Responses.swift	95.00% <ø> (ø)
Sources/ParseSwift/Protocols/ParseTypeable.swift	90.90% <ø> (+35.35%)	⬆️
Sources/ParseSwift/Protocols/Objectable.swift	91.66% <92.00%> (-6.30%)	⬇️
Sources/ParseSwift/Objects/ParseObject.swift	90.95% <100.00%> (ø)
Sources/ParseSwift/Objects/ParseUser.swift	93.48% <100.00%> (ø)

... and 6 files with indirect coverage changes