<!-- 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
**Root Cause:**
The current pipeline builds the entire solution and runs all UI tests
every time, which takes more than 2 hours to complete.
**Fix**
Make the PowerToys UI test pipeline provides flexible options for
building and testing:
### Pipeline Options
- **useLatestOfficialBuild**: When checked, downloads the latest
official PowerToys build and installs it for testing. This skips the
full solution build and only builds UI test projects.
- **useCurrentBranchBuild**: When checked along with
`useLatestOfficialBuild`, downloads the official build from the current
branch instead of main.
- **uiTestModules**: Specify which UI test modules to build and run.
Examples:
- `UITests-FancyZones` - Only FancyZones UI tests
- `MouseUtils.UITests` - Only MouseUtils UI tests
- `['UITests-FancyZones', 'MouseUtils.UITests']` - Multiple specific
modules
- Leave empty to build and run all UI test modules
### Build Modes
1. **Official Build + Selective Testing** (`useLatestOfficialBuild =
true`)
- Downloads and installs official PowerToys build
- Builds only specified UI test projects
- Runs specified UI tests against installed PowerToys
- Controlled by `uiTestModules` parameter
2. **Full Build + Testing** (`useLatestOfficialBuild = false`)
- Builds entire PowerToys solution
- Builds UI test projects (all or specific based on `uiTestModules`)
- Runs UI tests (all or specific based on `uiTestModules`)
- Uses freshly built PowerToys for testing
<!-- 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
- [x] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [x] **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
