MudBaseInput: Make OnBlurred async

[ScarletKuro]

Description

Fixes: #6322
Wasn't catching exception since on blurr wasn't awaited (async void problem)

I believe since OnBlurred was protected internal it's not breaking change to change the signature

How Has This Been Tested?

New unit test + checked visually on https://try.mudblazor.com/snippet/QOwdkmvIplIxkslV

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• The PR is submitted to the correct branch (dev).
• My code follows the code style of this project.
• I've added relevant tests.

[ScarletKuro]

Doesn't fixes the KeyDown down since the method isn't internal in MudBaseInput

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.11 ⚠️

Comparison is base (49e627a) 90.63% compared to head (80db3af) 90.53%.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #6633      +/-   ##
==========================================
- Coverage   90.63%   90.53%   -0.11%     
==========================================
  Files         399      399              
  Lines       13587    13613      +26     
==========================================
+ Hits        12315    12324       +9     
- Misses       1272     1289      +17     

Impacted Files	Coverage Δ
src/MudBlazor/Components/Input/MudRangeInput.razor	85.71% <ø> (ø)
...azor/Components/NumericField/MudNumericField.razor	100.00% <ø> (ø)
.../MudBlazor/Components/TextField/MudTextField.razor	100.00% <ø> (ø)
src/MudBlazor/Base/MudBaseInput.cs	92.30% <100.00%> (ø)
src/MudBlazor/Base/MudFormComponent.cs	83.33% <100.00%> (-4.49%)	⬇️
src/MudBlazor/Components/Input/MudInput.razor	100.00% <100.00%> (ø)
src/MudBlazor/Components/Mask/MudMask.razor	100.00% <100.00%> (ø)
src/MudBlazor/Components/Mask/MudMask.razor.cs	94.90% <100.00%> (ø)
...r/Components/NumericField/MudNumericField.razor.cs	98.71% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[ScarletKuro]

It seems that my recent change resulted in a breaking change for those who inherit this type and previously used OnBlurred. I take full responsibility for this mistake. I was confused by the use of the word "internal" in the method signature and wrongly assumed that it would be a safe change since I thought the method was only visible within the library. However, it turns out that the method is actually marked as protected internal, which makes it visible to anyone who inherits MudBaseInput.
https://stackoverflow.com/questions/585859/what-is-the-difference-between-protected-and-protected-internal

[henon]

Well, the break already happened, and we don't guarantee that protected API won't be changed, so I think no revert is necessary.