Refactor StrongNumber Activity / ViewModel to use single view state

[xizzhu]

Essentially part of #233, which is too big to manage.

[codecov-commenter]

Codecov Report

Merging #237 (af4786a) into master (d83a067) will increase coverage by 0.09%.
The diff coverage is 35.54%.

@@            Coverage Diff             @@
##           master     #237      +/-   ##
==========================================
+ Coverage   52.74%   52.83%   +0.09%     
==========================================
  Files         122      125       +3     
  Lines        4609     4705      +96     
  Branches      605      618      +13     
==========================================
+ Hits         2431     2486      +55     
- Misses       2105     2145      +40     
- Partials       73       74       +1     

Impacted Files	Coverage Δ
.../main/kotlin/me/xizzhu/android/joshua/Injection.kt	0.00% <0.00%> (ø)
...android/joshua/core/CoroutineDispatcherProvider.kt	0.00% <0.00%> (ø)
...n/me/xizzhu/android/joshua/infra/BaseActivityV2.kt	0.00% <0.00%> (ø)
...ndroid/joshua/strongnumber/StrongNumberActivity.kt	0.00% <0.00%> (ø)
.../main/kotlin/me/xizzhu/android/joshua/ui/Dialog.kt	0.00% <0.00%> (ø)
...e/xizzhu/android/joshua/preview/PreviewViewData.kt	96.77% <87.50%> (+20.91%)	⬆️
.../me/xizzhu/android/joshua/infra/BaseViewModelV2.kt	100.00% <100.00%> (ø)
...droid/joshua/strongnumber/StrongNumberViewModel.kt	98.70% <100.00%> (+12.65%)	⬆️

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