Always include traits in event payload, even if empty.

[bsneed]

• Made traits non-optional in state.
• Updated call points to provide an empty object where it was nil.
• Updated tests to accurately test fresh instance as well as reset.
• Removed out of date Windows/Linux tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.13%. Comparing base (59ae167) to head (77bdd7e).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #384      +/-   ##
==========================================
- Coverage   71.12%   70.13%   -1.00%     
==========================================
  Files          48       48              
  Lines        4894     4795      -99     
==========================================
- Hits         3481     3363     -118     
- Misses       1413     1432      +19     

Files with missing lines	Coverage Δ
Sources/Segment/Analytics.swift	84.52% <100.00%> (-0.41%)	⬇️
Sources/Segment/State.swift	95.87% <100.00%> (-2.07%)	⬇️

... and 20 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.