Always On Top: The opacity should be able to configure the hotkey individually (#46410)

<!-- 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
This pull request adds support for customizing the hotkeys used to
increase and decrease the opacity of pinned windows in the Always On Top
module.
Previously, these shortcuts were hardcoded to use the same modifiers as
the main pin hotkey.

With these changes, users can now independently configure the increase
and decrease opacity shortcuts via the settings UI, and the backend has
been updated to respect and store these new settings.

Another change: If window is not Always On Topped, the opacity change
take no effect, so we should not intercept, we should pass through to
minimize the impact.

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

- [X] Closes: #46391, #46387
<!-- - [ ] Closes: #yyy (add separate lines for additional resolved
issues) -->
- [ ] **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
<img width="1184" height="351" alt="image"
src="https://github.com/user-attachments/assets/5d20ffae-9f0c-4ce3-9d85-2ba1efea6301"
/>

<img width="336" height="244" alt="image"
src="https://github.com/user-attachments/assets/a78cc4a3-9eb3-49f1-bbb9-d6db37554e53"
/>

Verified locally that transparency hotkey will not intercept the normal
hotkey in window if Always on top not enabled

---------

Co-authored-by: Niels Laute <[email protected]>