[Installer] Upgrade the installer from WiX3 to WiX5 (#40877)

<!-- Enter a brief description/summary of your PR here. What does it
fix/what does it change/how was it tested (even manually, if necessary)?
-->
## Summary of the Pull Request
Background: The current PowerToys installer is built using Wix3, which
has now been deprecated. To improve security, service quality, and
community support, we’re upgrading the installer to Wix5.

Implementation:
Created Wix5-based projects(PowerToysSetupVext and
PowerToysSetupCustomActionsVNext) within the installer while retaining
the existing Wix3 project. Both versions are built to generate separate
installation packages. The Wix3-related code will be removed after
successful release testing confirms no issues.

Special case:
Wix5 has removed the property for 'ShowFilesInUse'. Now, whenever a file
is in use during installation, a FilesInUse pop-upwill automatically
appear asking for the next step. To ensure this doesn't interfere with
scenarios that require silent installation (e.g. Winget method), we’ve
handled it using the bafunction approach.



<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist

- [ ] Closes: #xxx
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

---------

Co-authored-by: Jerry Xu <n.xu@outlook.com>
Co-authored-by: Kai Tao <69313318+vanzue@users.noreply.github.com>
Co-authored-by: leileizhang <leilzh@microsoft.com>
Co-authored-by: Kai Tao (from Dev Box) <kaitao@microsoft.com>
Co-authored-by: vanzue <vanzue@outlook.com>

doc/devdocs/core/installer.md

@@ -1,6 +1,6 @@
 # PowerToys Installer
 
-## Installer Architecture (WiX 3)
+## Installer Architecture (WiX 3/ WiX 5)
 
 - Uses a bootstrapper to check dependencies and close PowerToys
 - MSI defined in product.wxs
@@ -22,7 +22,7 @@
 
 ### MSI Installer Build Process
 
-- First builds `PowerToysSetupCustomActions` DLL and signs it
+- First builds `PowerToysSetupCustomActions` DLL and signs it, for WiX5 project, installer will build `PowerToysSetupCustomActionsVNext` DLL.
 - Then builds the installer without cleaning, to reuse the signed DLL
 - Uses PowerShell scripts to modify .wxs files before build
 - Restores original .wxs files after build completes
@@ -135,6 +135,23 @@ If you prefer, you can alternatively build prerequisite projects for the install
 
 The resulting `PowerToysSetup.msi` installer will be available in the `installer\PowerToysSetup\x64\Release\` folder.
 
+For WiX3 project, run `Developer Command Prompt for VS 2022` in admin mode and execute the following command to build the installer. The generated installer package will be located at `\installer\PowerToysSetup\{platform}\Release\MachineSetup`.
+
+```
+git clean -xfd  -e *exe -- .\installer\
+MSBuild -t:restore  .\installer\PowerToysSetup.sln -p:RestorePackagesConfig=true /p:Platform="x64" /p:Configuration=Release
+MSBuild -m .\installer\PowerToysSetup.sln /t:PowerToysInstaller /p:Configuration=Release /p:Platform="x64" 
+MSBuild -m .\installer\PowerToysSetup.sln /t:PowerToysBootstrapper /p:Configuration=Release /p:Platform="x64" 
+```
+For WiX5 project, run `Developer Command Prompt for VS 2022` in admin mode and execute the following command to build the installer. The generated installer package will be located at `\installer\PowerToysSetupVNext\{platform}\Release\MachineSetup`.
+
+```
+git clean -xfd  -e *exe -- .\installer\
+MSBuild -t:restore  .\installer\PowerToysSetup.sln -p:RestorePackagesConfig=true /p:Platform="x64" /p:Configuration=Release
+MSBuild -t:Restore -m .\installer\PowerToysSetup.sln /t:PowerToysInstallerVNext /p:Configuration=Release /p:Platform="x64"
+MSBuild -t:Restore -m .\installer\PowerToysSetup.sln /t:PowerToysBootstrapperVNext /p:Configuration=Release /p:Platform="x64" 
+```
+
 ### Supported arguments for the .EXE Bootstrapper installer
 
 Head over to the wiki to see the [full list of supported installer arguments][installerArgWiki].