Revert "Update WindowsAppSDK to 1.8 (dotnet#32174)" (dotnet#33537)

Reverts the Windows App SDK update from version 1.7 to 1.8 introduced in
PR dotnet#32174.

## Reverted Changes

**Version downgrades:**
- `MicrosoftWindowsAppSDKPackageVersion`: `1.8.251106002` →
`1.7.250909003`
- `MicrosoftWindowsSDKBuildToolsPackageVersion`: `10.0.26100.4654` →
`10.0.22621.756`

**Package references removed:**
- `Microsoft.WindowsAppSDK` from `Essentials.csproj`,
`Graphics.Skia.csproj`, `Graphics.Win2D.csproj`

**Restored configurations:**
- `Controls.Xaml.csproj`: Re-added `WINDOWS` define constant and
`AppxGeneratePriEnabled=false`
- `Directory.Build.targets`: Removed
`GetTypeScriptCopyToOutputDirectoryItems` target
- `WindowsTemplateTest.cs`: Restored original RID-based asset path logic
- `windows.cake`: Restored `X509KeyUsageFlags.NonRepudiation` in
certificate generation

This reverts commit 5a39604.

> [!WARNING]
>
> <details>
> <summary>Firewall rules blocked me from connecting to one or more
addresses (expand for details)</summary>
>
> #### I tried to connect to the following addresses, but was blocked by
firewall rules:
>
> - `ghcr.io`
> - Triggering command: `/tmp/dependabot-cli/dependabot/dependabot
/tmp/dependabot-cli/dependabot/dependabot graph nuget org/repo --local
/home/REDACTED/work/maui/maui --branch main --directory
src/Controls/src/Xaml --proxy-cert
/home/REDACTED/work/_temp/runtime-logs/mkcert/rootCA.pem --updater-env
NODE_EXTRA_CA_CERTS=/usr/local/share/ca-certificates/dbot-ca.crt` (dns
block)
> - Triggering command: `/tmp/dependabot-cli/dependabot/dependabot
/tmp/dependabot-cli/dependabot/dependabot graph nuget org/repo --local
/tmp/dependabot-base-edeX71/repo --branch main --directory
src/Essentials/src --proxy-cert
/home/REDACTED/work/_temp/runtime-logs/mkcert/rootCA.pem --updater-env
NODE_EXTRA_CA_CERTS=/usr/local/share/ca-certificates/dbot-ca.crt` (dns
block)
> - Triggering command: `/tmp/dependabot-cli/dependabot/dependabot
/tmp/dependabot-cli/dependabot/dependabot graph nuget org/repo --local
/home/REDACTED/work/maui/maui --branch main --directory
src/Essentials/src --proxy-cert
/home/REDACTED/work/_temp/runtime-logs/mkcert/rootCA.pem --updater-env
NODE_EXTRA_CA_CERTS=/usr/local/share/ca-certificates/dbot-ca.crt` (dns
block)
>
> If you need me to access, download, or install something from one of
these locations, you can either:
>
> - Configure [Actions setup
steps](https://gh.io/copilot/actions-setup-steps) to set up my
environment, which run before the firewall is enabled
> - Add the appropriate URLs or hosts to the custom allowlist in this
repository's [Copilot coding agent
settings](https://github.com/dotnet/maui/settings/copilot/coding_agent)
(admins only)
>
> </details>

<!-- START COPILOT CODING AGENT SUFFIX -->



<!-- START COPILOT ORIGINAL PROMPT -->



<details>

<summary>Original prompt</summary>

> can you revert the following PR ?
dotnet#32174


</details>



<!-- START COPILOT CODING AGENT TIPS -->
---

✨ Let Copilot coding agent [set things up for
you](https://github.com/dotnet/maui/issues/new?title=✨+Set+up+Copilot+instructions&body=Configure%20instructions%20for%20this%20repository%20as%20documented%20in%20%5BBest%20practices%20for%20Copilot%20coding%20agent%20in%20your%20repository%5D%28https://gh.io/copilot-coding-agent-tips%29%2E%0A%0A%3COnboard%20this%20repo%3E&assignees=copilot)
— coding agent works faster and does higher quality work when set up for
your repo.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

[release/10.0.1xx-sr2] [iOS, macOS] Fixed CollectionView group header…

… size changes with ItemSizingStrategy (dotnet#33166)

Backport of dotnet#33161 to release/10.0.1xx-sr2

/cc @PureWeen @NanthiniMahalingam

---------

Co-authored-by: NanthiniMahalingam <105482474+NanthiniMahalingam@users.noreply.github.com>

[release/10.0.1xx-sr1] [ci] Revert changes setting Creator (dotnet#32803

)

Backport of dotnet#32743 to release/10.0.1xx-sr1

/cc @rmarinho

[release/10.0.1xx-sr1] Fix SafeAreaEdges.SoftInput applying bottom pa…

…dding when keyboard is hidden and inset consumption issue (dotnet#32448)

* Initial plan

* - Fix Bottom Inset when keyboard is closed

* Remove CurrentSettings element checks that were causing test timeouts

Co-authored-by: PureWeen <5375137+PureWeen@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Shane Neuville <shneuvil@microsoft.com>
Co-authored-by: PureWeen <5375137+PureWeen@users.noreply.github.com>

Update FlyoutViewHandler.Windows.cs (dotnet#32007)

Co-authored-by: devanathan-vaithiyanathan <114395405+devanathan-vaithiyanathan@users.noreply.github.com>

[release/9.0.1xx-sr11] [Windows] Revert cleanup of `AccessibilityExte…

…nsions` (dotnet#31758)

* revert

* test

---------

Co-authored-by: MartyIX <203266+MartyIX@users.noreply.github.com>

Revert "9.0.110 branding (dotnet#31527)" (dotnet#31528)

This reverts commit 109e247.