Add ability to add or update global properties

[IeuanWalker]

My used case:

In our app we have the ability to allow the user to set the language the app uses manually.

Currently, the code sets the language based on the current culture at startup -
https://github.com/dhindrik/TinyInsights.Maui/blob/f94ee43e1c771fa3ec4213e4afdaa10276db0b89/TinyInsights/ApplicationInsightsProvider.cs#L141C8-L141C115

This happens before we set the app to the users saved preferred language, and the user could change the language at any point.

Meaning the stats in the application doesn't reflect the actual app settings

There are 2 changes in this PR -

• Added UpsertGlobalProperty
  • This either Adds or Updates a property in the global properties dictionary.
  • i.e. i can use this to override the preset language insights.UpsertGlobalProperty("Language", AppSettings.SelectedLanguage)
  • It can also be used for other cases, f.e. we'd like to record the users theme so we can see whats the most used etc
• Update the language query on the dashboard
  • Add | summarize arg_max(timestamp, *) by user_Id
  • This gets the last pageView event for the user, without this even with just one user the dashboard was showing 2 languages being used -
    
  • It now just counts the latest language used by each user -
    

[dhindrik]

Great improvement! Thank you for contributing!