MudChart [TimeSeries]: Fix Types other than T="double" to work

[pkaaz]

Currently TimeSeries fails with types like int if it is set as T="int". At runtime it tries to convert TimeValue<int> to TimeValue<double> and just silently fails without drawing any of the points but making the skeleton of the chart. The culprit line:

MudBlazor/src/MudBlazor/Components/Chart/Charts/TimeSeries.razor.cs

Line 357 in e7235a7

return (TReturn)(object)data[dataPointIndex];

as it fails to convert (TimeValue<double>)(object)data[dataPointIndex] which is TimeValue<int>

(TReturn)(object)data[dataPointIndex] | '(TReturn)(object)data[dataPointIndex]' threw an exception of type 'System.InvalidCastException' | MudBlazor.Charts.TimeValue {System.InvalidCastException}

Example snippet
https://try.mudblazor.com/snippet/wkGKuRxPRsOzFKij

The fix changes double variables to generic T so it matches the Types. It also adds an IFormattable constraint to TNumber for TimeValue so .ToString() could be used for the TooltipLabelFormat and is already a requirement on T

Tests

• Tested on MudBlazor.Docs.Server - changing all the types to int and comparing the results to match
• Packaging the project and using where I needed it and it shows the correct result without resorting to conversions
• Running the current UnitTests - All passing, at least locally

Checklist:

• I've read the contribution guidelines
• My code follows the style of this project

---

• I've added or updated relevant unit tests

• I looked at the unit tests for other charts and they have no tests for Types except for DonutChart. I can try and add some if needed though.

[Anu6is]

Could you add a unit test for an integer chart?

[pkaaz]

I added a test for Integer that is basically Identical to the BasicExample one just with integer types as the data would remain the same. The old code throws this during this test:

Message: 
System.InvalidCastException : Unable to cast object of type 'MudBlazor.Charts.TimeValue`1[System.Int32]' to type 'MudBlazor.Charts.TimeValue`1[System.Double]'.

The PR code passes. Let me know if this is enough

[danielchalmers]

Thank you!