Fix for setting of BG Targets

[Sjoerd-Bo3]

Implemented the iAPS fix https://github.com/Artificial-Pancreas/iAPS/pull/715/files that closes Issue #318

[bjornoleh]

Approving based on testing with GH build.

Edit: Did check that there are no uncommitted changes after the build. But did not do significant code review.

Tested successfully setting mmol target values of:
4 (min)
4,1
6
6,1
6,2
10 (max)

Also tested with mg/dL units:
72 (min)
109
110
111
180 (max)

[marionbarker]

Summary

I confirm Issue #318 is fixed with this patch

Testing

Tested by applying patch to alpha commit 82f2d01

• built on existing Trio, SE running iOS 17.5.1
• units already mmol/L from testing the issue earlier (see comment)
  • modify target, save, go to settings, return to target screen:
    • choose 6.0; final 6.0
    • choose 6.1; final 6.1
    • choose 6.2; final 6.2
    • choose 4.0, final 4.0
    • choose 10.0, final 10.0

[dnzxy]

Bandaid fix for now, we generally a more thought out handling of mmol values; handle everything in mg/dl and only display in mmol.

This fixes #318 and LGTM. Merging with 3 approvals.