[Awake] Fix lack of process validation for --pid and --use-parent-pid options (#41803)

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fix/what does it change/how was it tested (even manually, if necessary)?
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## Summary of the Pull Request
This adds validation for the "PID binding" modes of Awake. Previously,
Awake did not validate that a user-supplied process ID actually
corresponded to a running process (leading to an infinite keep-awake
duration); nor did it validate that the parent process could be found
and bound to when using the `--use-parent-pid` option (which left Awake
in an unresponsive state without setting a keep-awake mode).

This PR fixes those issues by validating that the process exists when
using `--pid` (or when the PID comes from PowerToys Runner itself), and
also early-exits if the parent process cannot be bound to when using
`--use-parent-pid`.

This supersedes a prior PR which just fixes the
`--use-parent-pid`-related flaw, #41744.

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## PR Checklist

- [x] Closes: #41709, #41722
- [ ] **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
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pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
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- [ ] **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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## Detailed Description of the Pull Request / Additional comments
For the `--pid` fix, this is validated both when the command line is
parsed (by extending the existing `pidOption` validator) and just before
the process ID is bound to (in `HandleCommandLineArguments` and a new
`HandleProcessScopedKeepAwake` method). These use a new `ProcessExists`
method which checks that the process exists (funnily enough) and isn't
exiting.

I also added a very paranoid check that the process ID isn't Awake's
own. This couldn't be done deliberately, but if a user mis-typed their
desired PID and it happened to match Awake's, this would lead to an
indefinite keep-awake. It's a very remote possibility, but
one-in-ten-thousand odds still happen.

The fix for the `--use-parent-pid` checks the return value of the
`Manager.GetParentProcess` call, which was previously lacking, exiting
early if it sees a `0` failure value.

Added validation for PID value not being zero or negative.

There are new string resources for the general PID-binding failure and
the specific parent process binding issue. I don't actually know why
these are resources, but I followed the existing convention from the
project.


<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed
Tested that:
- When `null` (`0` when marshalled) is returned from the
`GetParentProcess` path that Awake exits early and does not enter its
failed state.
- When a non-existent PID is input via the `--pid` command line that
Awake exits early and does not attempt to bind to a non-existent
process.
- PID-binding still works without issue when a correct process ID is
provided on the command line.
- `--use-parent-pid` still works when the parent process can be located
and bound to.
- New PID-binding parameter checks are caught (0 or negative numbers are
rejected).
- Other modes still work as expected.

src/modules/awake/Awake/Properties/Resources.resx

@@ -226,4 +226,13 @@
   <data name="AWAKE_SCREEN_OFF" xml:space="preserve">
     <value>Off</value>
   </data>
+  <data name="AWAKE_EXIT_PARENT_BINDING_FAILURE_MESSAGE" xml:space="preserve">
+    <value>Exiting because the parent process ID could not be found.</value>
+  </data>
+  <data name="AWAKE_EXIT_PROCESS_BINDING_FAILURE_MESSAGE" xml:space="preserve">
+    <value>Exiting because the requested process ID could not be found.</value>
+  </data>
+  <data name="AWAKE_EXIT_BIND_TO_SELF_FAILURE_MESSAGE" xml:space="preserve">
+    <value>Exiting because the provided process ID is Awake's own.</value>
+  </data>
 </root>