Font loading impacts Windows desktop startup

[jonathanpeppers]

Description

~66ms is spent on my PC just loading fonts:

This was a dotnet new maui template, that has 2 fonts listed.

Speedscope file: PerfViewData.View1.perfView.xml.speedscope.json.zip

Public API Changes

n/a

Intended Use-Case

I think we could cut down the ~66ms spent by some order of magnitude.

[MartyIX]

(Sent over Discord, but maybe it's of some use even on Github)

I created https://github.com/MartyIX/maui/tree/feature/2024-03-14-font-testing (MartyIX@c1d76bc) where I add Ubuntu fonts and show 3 labels + there is a button to add a new label.

The Debug.WriteLine calls return:

XXX [FontManager.Windows.CreateFontFamily] CreateFontFamily UbuntuRegular
XXX [FontManager.Windows.CreateFontFamily] 201 ms ('formatted' length is 36 characters)
XXX [TextBlockExtensions.UpdateFont] FontManager.GetFontFamily executed in 213 ms.
XXX [TextBlockExtensions.UpdateFont] FontManager.GetFontFamily executed in 0 ms.
XXX [TextBlockExtensions.UpdateFont] FontManager.GetFontFamily executed in 0 ms.

(It was run in the Debug configuration though.)

The sample was done to show what happens when new Labels are added to the screen when the app is already started.

[MartyIX]

This PR #22782 would make this better not only for startup but even for the rest of an app's lifetime.