Fixed issue through adding onLayerViewStatechanged on MapView

[NourdotSiwar]

Description

PR to fix a Kotlin sample "GENERATE_OFFLINE_MAP" in EDIT_AND_MANAGE_DATA category.

Links and Data

Sample Epic: runtime/kotlin/issues/ISSUE_NUMBER

• a vTest Job for this PR has been run
  • [x] link: https://runtime-kotlin.esri.com/view/all/job/vtest/job/sampleviewer/

What To Review

• Review the changed/added code to make sure the changes wouldn't impact anything else and to see if sample code is easy to read.
• MainScreen.kt and MapViewModel.kt files

How to Test

Run the sample on the sample viewer or the repo.

1. When running it, the red border should always show on launch
2. After generating the offline map, and resettiing the map, the red border should show and stay the same size.