Drop older Swift version (<5.8), Bump deployment targets to support minimums

[ffried]

New Pull Request Checklist

• I have read and understood the CONTRIBUTING guide
• I have read the Documentation
• I have searched for a similar pull request in the project and found none

• I have updated this branch with the latest master to avoid conflicts (via merge from master or rebase)
• I have added the required tests to prove the fix/feature I am adding
• I have updated the documentation (if necessary)
• I have run the tests and they pass
• I have run the lint and it passes (pod lib lint)

This merge request fixes / refers to the following issues: Fixes #1375, fixes #1404

Pull Request Description

• Drops support for older Swift versions pre 5.8 (SPM will automatically fall back to older releases).
• Bumps deployment targets to minimums supported by Xcode 15.

[ffried]

This also fixes #1375 since I bumped the minimum to watchOS 5.0...

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.17%. Comparing base (34f5901) to head (8d18208).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1416      +/-   ##
==========================================
+ Coverage   52.24%   56.17%   +3.92%     
==========================================
  Files          32       34       +2     
  Lines        4580     4840     +260     
  Branches      518      518              
==========================================
+ Hits         2393     2719     +326     
+ Misses       2187     2121      -66     

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