feat: add revertKeyPath() and revertObject() methods to ParseObject

[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

After a developer begins mutating/updating a ParseObject that already has an objectId via mergeable or some other method that allows the developer to save the ParseObject using the Parse Servers quirky patch. The only way to revert a specific KeyPath back to its original value is by setting it based on a local stored version or remembering what that value was.

Related issue: #n/a

Approach

Leverage the originalData property to allow developers to revert specific KeyPath's or the whole ParseObject.

Example usage:

/* 
Assuming `score` is a GameScore `ParseObject` which was already saved and has the following properties:
- objectId = "yolo"
- name = "Frazier"
- points = 19
- ...
*/

// Reverting the whole object
var mutableScore = score.mergeable
mutableScore.points = 50
mutableScore.player = "Ali"         
mutableScore = try mutableScore.revertObject()
print(mutableScore == score) // true

// Reverting a specific KeyPath
var mutableScore2 = score.mergeable
mutableScore2.points = 50
mutableScore2.player = "Ali"         
mutableScore2 = try mutableScore2.revertKeyPath(\.player)
print(mutableScore2 == score) // false
print(mutableScore2 == mutableScore) // false
print(mutableScore2.player == score.player) // true
print(mutableScore2.player == mutableScore.player) // true

TODOs before merging

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

[parse-github-assistant[bot]]

Thanks for opening this pull request!

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

[codecov[bot]]

Codecov Report

Merging #402 (b9552e1) into main (106f97d) will increase coverage by 0.00%. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #402   +/-   ##
=======================================
  Coverage   89.64%   89.65%           
=======================================
  Files         158      158           
  Lines       15081    15113   +32     
=======================================
+ Hits        13519    13549   +30     
- Misses       1562     1564    +2     

Impacted Files	Coverage Δ
Sources/ParseSwift/Objects/ParseObject.swift	87.73% <100.00%> (+0.28%)	:arrow_up:

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