test: Fix unit tests and add isLaunch test

[einsteinx2]

Summary

I found that there was an MPBackgroundController unit test called testPreviousForegroundTime that was failing only on Github due to the way it was implemented. While investigating that, I found that I had the isLaunch boolean backwards, and it should also have its own unit test.

I also noticed that some tests were disabled for tvOS when there's no reason for that as the behavior should be the same, so I enabled them.

I also fixed how some of the other tests were implemented regarding messageQueue threading.

Testing Plan

• Confirmed via breakpoints when running the previousForgroundTime test that the assertions are hitting correctly now
• Tested isLaunch behavior in a test app locally and new unit test added

• Confirmed all tests run on tvOS as well

  Reference Issue (For mParticle employees only. Ignore if you are an outside contributor)

  • Closes https://go.mparticle.com/work/SQDSDKS-5981

[mparticle-automation]

:tada: This PR is included in version 8.17.0 :tada:

The release is available on GitHub release

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