CmdPal: Align spellchecker and naming to .NET guidelines (#43974)

## Summary of the Pull Request

- Add command-line parameter value (icf)
- Unify file and class name casing to match .NET naming conventions (RDP
-> Rdp as Url, Dns, Xml) -- fixes IRDP spellchecking error
- Rename IRdpConnectionManager to IRdpConnectionsManager (*s) to match
the class name

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

- [ ] Closes: #xxx
<!-- - [ ] 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/Tests/Microsoft.CmdPal.Ext.RemoteDesktop.UnitTests/FallbackRemoteDesktopItemTests.cs

@@ -113,10 +113,10 @@ public class FallbackRemoteDesktopItemTests
         return field.GetValue(command) as string ?? string.Empty;
     }
 
-    private static (FallbackRemoteDesktopItem Fallback, IRdpConnectionManager Manager) CreateFallback(params string[] connectionNames)
+    private static (FallbackRemoteDesktopItem Fallback, IRdpConnectionsManager Manager) CreateFallback(params string[] connectionNames)
     {
         var settingsManager = new MockSettingsManager(connectionNames);
-        var connectionsManager = new MockRDPConnectionsManager(settingsManager);
+        var connectionsManager = new MockRdpConnectionsManager(settingsManager);
 
         var fallback = new FallbackRemoteDesktopItem(connectionsManager);
 

src/modules/cmdpal/Tests/Microsoft.CmdPal.Ext.RemoteDesktop.UnitTests/MockRdpConnectionsManager.cs

@@ -10,13 +10,13 @@ using Microsoft.CmdPal.Ext.RemoteDesktop.Settings;
 
 namespace Microsoft.CmdPal.Ext.RemoteDesktop.UnitTests;
 
-internal sealed class MockRDPConnectionsManager : IRdpConnectionManager
+internal sealed class MockRdpConnectionsManager : IRdpConnectionsManager
 {
     private readonly List<ConnectionListItem> _connections = new();
 
     public IReadOnlyCollection<ConnectionListItem> Connections => _connections.AsReadOnly();
 
-    public MockRDPConnectionsManager(ISettingsInterface settingsManager)
+    public MockRdpConnectionsManager(ISettingsInterface settingsManager)
     {
         _connections.AddRange(settingsManager.PredefinedConnections.Select(ConnectionHelpers.MapToResult));
     }

src/modules/cmdpal/Tests/Microsoft.CmdPal.Ext.RemoteDesktop.UnitTests/RdpConnectionsManagerTests.cs

@@ -10,13 +10,13 @@ using Microsoft.VisualStudio.TestTools.UnitTesting;
 namespace Microsoft.CmdPal.Ext.RemoteDesktop.UnitTests;
 
 [TestClass]
-public class RDPConnectionsManagerTests
+public class RdpConnectionsManagerTests
 {
     [TestMethod]
     public void Constructor_AddsOpenCommandItem()
     {
         // Act
-        var manager = new RDPConnectionsManager(new MockSettingsManager(["test.local"]));
+        var manager = new RdpConnectionsManager(new MockSettingsManager(["test.local"]));
 
         // Assert
         Assert.IsTrue(manager.Connections.Any(item => string.IsNullOrEmpty(item.ConnectionName)));