CmdPal: Make Indexer great again - part 1 - hotfix (#44729)

## Summary of the Pull Request

This PR introduces a rough hotfix for several indexer-related issues.

- Premise: patch what we can in-place and fix the core later (reworking
`SeachEngine` and `SearchQuery` is slightly trickier). This patch also
removes some dead code for future refactor.
- Adds search cancellation to the File Search page and the indexer
fallback.
- Prevents older searches from overwriting newer model state and reduces
wasted work.
- Stops reusing the search engine; creates a new instance per search to
avoid synchronization issues.
- That `SeachEngine` and `SearchQuery` are not multi-threading friendly.
- Removes search priming to simplify the code and improve performance.
- Since `SearchQuery` cancels and re-primes on every search, priming
provides little benefit and can hide extra work (for example,
cancellation triggering re-priming).
- Fixes the indexer fallback subject line not updating when there is
more than one match.
  - It previously kept the old value, which was confusing.
- ~Shows the number of matched files in the fallback result.~
- Fetching total number of rows was reverted, performance was not stable
:(
- Optimizes the indexer fallback by reducing the number of items
processed but not used.
- Only fetches the item(s) needed for the fallback itself—no extra work
on the hot path.
- Stops reusing the fallback result when navigating to the File Search
page to show more results. This requires querying again, but it
simplifies the flow and keeps components isolated.
- Fixes the English mnemonic keyword `kind` being hardcoded in the
search page filter. Windows Search uses localized mnemonic keyword
names, so this PR replaces it with canonical keyword `System.Kind` that
is universaly recognized.
- Adds extra diagnostics to `SearchQuery` and makes logging more
precise.
- DataPackage for the IndexerListItem now defers including of storage
items - boost performance and we avoid touching the item until its
needed.
- IndexerPage with a prepopulated query will delay loading until the
items are actually enumerated (to avoid populating from fallback hot
path) and it no longer takes external SearchEngine. It just recreates
everything.

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

- [x] Related to: #44728
- [x] Closes: #44731
- [x] Closes: #44732
- [x] Closes: #44743
<!-- - [ ] 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

src/modules/cmdpal/ext/Microsoft.CmdPal.Ext.Indexer/Properties/Resources.Designer.cs

@@ -19,7 +19,7 @@ namespace Microsoft.CmdPal.Ext.Indexer.Properties {
     // class via a tool like ResGen or Visual Studio.
     // To add or remove a member, edit your .ResX file then rerun ResGen
     // with the /str option, or rebuild your VS project.
-    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Resources.Tools.StronglyTypedResourceBuilder", "17.0.0.0")]
+    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Resources.Tools.StronglyTypedResourceBuilder", "18.0.0.0")]
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute()]
     [global::System.Runtime.CompilerServices.CompilerGeneratedAttribute()]
     internal class Resources {
@@ -177,6 +177,15 @@ namespace Microsoft.CmdPal.Ext.Indexer.Properties {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to The query matches multiple items.
+        /// </summary>
+        internal static string Indexer_Fallback_MultipleResults_Subtitle {
+            get {
+                return ResourceManager.GetString("Indexer_Fallback_MultipleResults_Subtitle", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Search for &quot;{0}&quot; in files.
         /// </summary>

src/modules/cmdpal/ext/Microsoft.CmdPal.Ext.Indexer/Properties/Resources.resx

@@ -211,4 +211,7 @@ You can try searching all files on this PC or adjust your indexing settings.</va
   <data name="Indexer_Command_Peek_Failed" xml:space="preserve">
     <value>Failed to launch Peek</value>
   </data>
+  <data name="Indexer_Fallback_MultipleResults_Subtitle" xml:space="preserve">
+    <value>The query matches multiple items</value>
+  </data>
 </root>