Globals: Add `DialogDefaults.DefaultFocus`, Consolidate others to their own static classes

[danielchalmers]

Description

How Has This Been Tested?

Type of Changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [X] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Documentation (fix or improvement to the website or code docs)

Checklist

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

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 73.33333% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 90.04%. Comparing base (28bc599) to head (b205a85). Report is 127 commits behind head on dev.

Files	Patch %	Lines
src/MudBlazor/Services/MudGlobal.cs	55.55%	4 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #8831 +/- ## ========================================== + Coverage 89.82% 90.04% +0.21% ========================================== Files 412 421 +9 Lines 11878 12292 +414 Branches 2364 2437 +73 ========================================== + Hits 10670 11068 +398 + Misses 681 672 -9 - Partials 527 552 +25 ```

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[henon]

In principle yes, it makes sense to have global defaults for every parameter, even those of MudDialog. I first thought, this would be better suited for DialogOptions but then, it is a parameter of a component and thus the default value would be expected to be customizable like all the other component parameters.

[henon]

When we add defaults for all components, there will be hundreds of definitions in MudGlobal. It might become quite unmanageable. You sure we shouldn't make static subclasses of MudGlobal for every component?

i.e. MudGlobal.DialogDefaults.DefaultFocus = ... MudGlobal.ButtonDefaults.Variant = ...

[danielchalmers]

@henon Do you want to implement your vision for that API separately and I rebase? Or tell me what the classes would look like and I can do it in this PR?

[henon]

public static class MudGlobal {
  public static class DialogDefaults { 
    public DefaultFocus DefaultFocus = DefaultFocus.Element;
  }
  public static class ButtonDefaults { 
    public static Variant Variant = Variant.Text;
  }
}

[danielchalmers]

@henon Done. Take a look now.

[henon]

Here is another idea, add these on top of what you already have:

    public static class OverlayDefaults
    {
        /// <summary>
        /// The default transition delay for <see cref="MudOverlay"/> and <see cref="MudPicker{T}"/>.
        /// </summary>
        public static TimeSpan Delay { get; set; } = TransitionDefaults.Delay;

        /// <summary>
        /// The default transition time for components like <see cref="MudTooltip"/>, <see cref="MudOverlay"/>, <see cref="MudPicker{T}"/>.
        /// </summary>
        public static TimeSpan Duration { get; set; } = TransitionDefaults.Duration;
    }

    public static class PickerDefaults
    {
        /// <summary>
        /// The default transition delay for <see cref="MudOverlay"/> and <see cref="MudPicker{T}"/>.
        /// </summary>
        public static TimeSpan Delay { get; set; } = TransitionDefaults.Delay;

        /// <summary>
        /// The default transition time for components like <see cref="MudTooltip"/>, <see cref="MudOverlay"/>, <see cref="MudPicker{T}"/>.
        /// </summary>
        public static TimeSpan Duration { get; set; } = TransitionDefaults.Duration;
    }

    public static class TooltipDefaults
    {
        /// <summary>
        /// The default transition delay for <see cref="MudOverlay"/> and <see cref="MudPicker{T}"/>.
        /// </summary>
        public static TimeSpan Delay { get; set; } = TransitionDefaults.Delay;

        /// <summary>
        /// The default transition time for components like <see cref="MudTooltip"/>, <see cref="MudOverlay"/>, <see cref="MudPicker{T}"/>.
        /// </summary>
        public static TimeSpan Duration { get; set; } = TransitionDefaults.Duration;
    }

That way, on top of changing the delay and transition duration for all via TransitionDefaults we can also set them differently for overlay, picker and tooltip.

[danielchalmers]

@henon Good idea. Added.