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

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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.



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## 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

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or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

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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>

.github/actions/spell-check/allow/code.txt

@@ -56,6 +56,8 @@ YVU
 YVYU
 zipfolder
 CODEOWNERS
+VNext
+vnext
 
 # FONTS
 
@@ -98,13 +100,25 @@ svgl
 
 altdown
 BUTTONUP
+bafunctions
+Baf
+Bitness
+BUILDARCHSHORT
 CTRLALTDEL
 Ctrls
+CSilent
+CBal
+CREATEBAFUNCTIONS
+CPrereq
+dirutil
+DUtil
+Editbox
 EXSEL
 HOLDENTER
 HOLDESC
 HOLDSPACE
 HOLDBACKSPACE
+IDIGNORE
 KBDLLHOOKSTRUCT
 keyevent
 LAlt
@@ -116,12 +130,16 @@ LCONTROL
 LCtrl
 LEFTDOWN
 LEFTUP
+locutil
+logutil
+msimg
 MBUTTON
 MBUTTONDBLCLK
 MBUTTONDOWN
 MBUTTONUP
 MIDDLEDOWN
 MIDDLEUP
+memutil
 NCRBUTTONDBLCLK
 NCRBUTTONDOWN
 NCRBUTTONUP
@@ -134,8 +152,18 @@ RCONTROL
 RCtrl
 RIGHTDOWN
 RIGHTUP
+Richedit
+rgwz
+resrutil
+srd
+scz
+shelutil
+thmutil
+uriutil
 VKTAB
+wcautil
 winkey
+wininet
 WMKEYDOWN
 WMKEYUP
 WMSYSKEYDOWN
@@ -145,6 +173,7 @@ XBUTTONDBLCLK
 XBUTTONDOWN
 XBUTTONUP
 XDOWN
+xmlutil
 
 # Prefix
 pcs