refactor: Address Swift 5.8 warnings

[cbaker6]

New Pull Request Checklist

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

Issue Description

Xcode 14.3 and Swift 5.8 introduced a number of new warnings when building the project.

Approach

Remove all warnings and use new await fulfillment(of: [expectation1], timeout: 20.0) instead of wait(for: [expectation1], timeout: 20.0) for async tests as there's a known deadlock issue with XCTestCase.wait in Xcode <=14.2. See 14.3 changelog for reference.

TODOs before merging

• Add tests
• Add entry to changelog

[codecov]

Codecov Report

Merging #90 (b806145) into main (a790bb7) will increase coverage by 0.43%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #90      +/-   ##
==========================================
+ Coverage   90.95%   91.38%   +0.43%     
==========================================
  Files         172      172              
  Lines       15209    15261      +52     
==========================================
+ Hits        13834    13947     +113     
+ Misses       1375     1314      -61     

Impacted Files	Coverage Δ
Sources/ParseSwift/Storage/KeychainStore.swift	93.71% <100.00%> (+0.83%)	⬆️
Sources/ParseSwift/Storage/ParseFileManager.swift	92.51% <100.00%> (-0.31%)	⬇️

... and 9 files with indirect coverage changes

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