DataGrid: optimize utility allocations

[stsrki]

We need to reuse constant utility values by creating read-only, or const members in code. The main problem with too many utilities is that for heavy components like DataGrid, it will allocate a new instance of each "fluent" method on each render. Usually, this is not a problem for simple use cases.

For example for:

• Display="Display.None" we can have Display="Constants.DisplayNone"
• Margin="@Blazorise.Margin.Is1.FromEnd" we can have Margin="Constants.Margin1FromEnd"

Where:

static class Constants
{
    public static readonly IFluentDisplay DisplayNone = Display.None;

    public static readonly IFluentSpacing Margin1FromEnd = Margin.Is1.FromEnd;

    // etc.
}