Use system credential storage on Windows

[VMelnalksnis]

Changes proposed in this pull request:

• Use Credential Manager for storing refresh token/credentials on windows (Use system credential manager to store refresh token/credentials #497)
• Refactor IsBusy

[codecov]

Codecov Report

Merging #500 (836dc7b) into master (1d5e67d) will decrease coverage by 3.60%.
The diff coverage is 38.11%.

@@            Coverage Diff             @@
##           master     #500      +/-   ##
==========================================
- Coverage   66.62%   63.01%   -3.61%     
==========================================
  Files         280      284       +4     
  Lines        8465     8507      +42     
  Branches      546      552       +6     
==========================================
- Hits         5640     5361     -279     
- Misses       2647     2973     +326     
+ Partials      178      173       -5     

Impacted Files	Coverage Δ
...lonia.Core/Authentication/AuthenticationService.cs	0.00% <0.00%> (-50.00%)	⬇️
...ade.Avalonia.Core/Authentication/LoginViewModel.cs	0.00% <0.00%> (-9.38%)	⬇️
...Core/Configuration/ApplicationSettingsViewModel.cs	0.00% <0.00%> (-29.27%)	⬇️
...meshade.Avalonia.Core/Configuration/OidcOptions.cs	0.00% <0.00%> (-42.86%)	⬇️
...nia.Core/DesignTime/DesignTimeCredentialStorage.cs	0.00% <0.00%> (ø)
...meshade.Avalonia.Core/DesignTime/DesignTimeData.cs	0.00% <0.00%> (-97.68%)	⬇️
...nomeshade.Avalonia.Core/Imports/ImportViewModel.cs	0.00% <0.00%> (-15.16%)	⬇️
...ce/Gnomeshade.Avalonia.Core/MainWindowViewModel.cs	0.00% <0.00%> (-6.17%)	⬇️
...de.Avalonia.Core/Reports/BalanceReportViewModel.cs	0.00% <0.00%> (-89.88%)	⬇️
...e.Avalonia.Core/Reports/CategoryReportViewModel.cs	0.00% <0.00%> (-68.89%)	⬇️
... and 60 more

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