Allow generic return types for ParseCloud, hint, and explain

[cbaker6]

Removes the return type of AnyCodable and allows the developer to specify the return type for ParseCloud, query hint and explain. This allows for leveraging the JSONDecoder instead of having to cast.

These are breaking changes

• Allow generic return types
• Fix testcases
• Fix playground examples
• Fix documentation
• Changed functionality of synchronous query.first(). It use to return nil if no values are found. Now it will throw an error if none are found. The asynchronous version already does this, this changes makes them behave the same.
• Prepare for 1.2.0 release

[codecov]

Codecov Report

Merging #92 (5a68dd9) into main (0b0d775) will decrease coverage by 0.14%.
The diff coverage is 72.60%.

@@            Coverage Diff             @@
##             main      #92      +/-   ##
==========================================
- Coverage   79.08%   78.94%   -0.15%     
==========================================
  Files          63       63              
  Lines        5115     5114       -1     
==========================================
- Hits         4045     4037       -8     
- Misses       1070     1077       +7     

Impacted Files	Coverage Δ
Sources/ParseSwift/API/Responses.swift	67.39% <ø> (ø)
Sources/ParseSwift/Objects/ParseInstallation.swift	82.60% <0.00%> (-0.18%)	⬇️
Sources/ParseSwift/Objects/ParseUser.swift	76.45% <0.00%> (-0.30%)	⬇️
Sources/ParseSwift/Protocols/Queryable.swift	0.00% <ø> (ø)
Sources/ParseSwift/Objects/ParseObject.swift	77.17% <16.66%> (-0.76%)	⬇️
Sources/ParseSwift/Types/Query.swift	90.63% <85.71%> (-0.08%)	⬇️
Sources/ParseSwift/API/URLSession+extensions.swift	80.21% <87.50%> (+1.64%)	⬆️
Sources/ParseSwift/API/API+Commands.swift	82.72% <100.00%> (ø)
Sources/ParseSwift/Coding/ParseCoding.swift	89.13% <100.00%> (+2.17%)	⬆️
...ources/ParseSwift/Storage/ParseKeyValueStore.swift	88.00% <100.00%> (ø)
... and 7 more

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