MudInput: Replace AutoGrow with Sizing

[danielchalmers]

Preparation for #8687

This pull request refactors and enhances the multiline and auto-growing text field functionality in MudBlazor. The main change is the replacement of the AutoGrow property with a more flexible Sizing property, allowing explicit control between fixed and auto-sizing behavior. The documentation and tests have been updated to reflect this new approach, and new test components have been added to demonstrate and validate the changes.

/// <summary>
/// The strategy for how the input calculates its height.
/// </summary>
public enum InputSizing
{
    /// <summary>
    /// The height is fixed based on the Lines property.
    /// </summary>
    [Description("fixed")]
    Fixed,

    /// <summary>
    /// The height grows and shrinks dynamically to fit the text content.
    /// Uses Lines as minimum and MaxLines as maximum.
    /// </summary>
    /// <remarks>
    /// Previously known as "AutoGrow".
    /// </remarks>
    [Description("auto")]
    Auto,
}

Checklist:

• I've read the contribution guidelines
• My code follows the style of this project
• I've added or updated relevant unit tests