Refactor Codebase

[karkarl]

Refactor WinUI-Gallery codebase:

### Tasks
- [x] Remove unused code
- [x] remove outdated ThemeResources
- [x] Proper xaml formatting
- [x] Proper class name / namespaces
- [x] Accessibility pass
- [x] Clean out unnecessary branches
- [x] Re-name `NewControls*` to `Home`
- [ ] https://github.com/microsoft/WinUI-Gallery/issues/1445
- [ ] https://github.com/microsoft/WinUI-Gallery/issues/1542

[Jay-o-Way]

Spring clean-up 🧹🪣🧽😛

[Jay-o-Way]

@niels9001 Would this include - for example - the following?

WinUI-Gallery/WinUIGallery/SettingsPage.xaml

Lines 12 to 20 in 0a300bf

	<!-- Style (inc. the correct spacing) of a section header -->
	<Style
	x:Key="SettingsSectionHeaderTextBlockStyle"
	BasedOn="{StaticResource BodyStrongTextBlockStyle}"
	TargetType="TextBlock">
	<Style.Setters>
	<Setter Property="Margin" Value="1,29,0,5" />
	</Style.Setters>
	</Style>

Those numbers are not by the book; the elements (TextBlock) can probably be replaced with more modern implementations via SettingsGroup (Header)

[karkarl]

@Jay-o-Way Yes - the idea is to have WinUI Gallery also be a useful repo to refer to for best coding practices. That includes updating redundant xaml.

[Jay-o-Way]

Also a nit I found:

WinUI-Gallery/WinUIGallery/SectionPage.xaml

Line 40 in 0a300bf

<Setter Target="TitleTxt.Style" Value="{StaticResource SubtitleTextBlockStyle}" />

is unneeded - actually conflicting with line 49: Style="{StaticResource TitleTextBlockStyle}"

---

Is it better to define style with Setters or in-element?