Update FluentUI to 4.11.9

[JamesNK]

Description

• Remove FluentSelect hack that has been fixed in library
• Use new try get methods with icons to avoid errors

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
  • No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
  • No
• Did you add public API?
  • Yes
    • If yes, did you have an API Review for it?
      • Yes
      • No
    • Did you add <remarks /> and <code /> elements on your triple slash comments?
      • Yes
      • No
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
    • If yes, have you done a threat model and had a security review?
      • Yes
      • No
  • No
• Does the change require an update in our Aspire docs?
  • Yes
    • Link to aspire-docs issue (consider using one of the following templates):
      • New (or update) doc-idea template
      • New breaking-change template
      • New diagnostic template
  • No

[Copilot]

Pull Request Overview

This PR updates FluentUI dependencies to 4.11.9, refactors icon resolution to use the new TryGetInstance pattern, and removes the temporary FixedFluentCombobox workaround in favor of the built-in component.

• Bump Microsoft.FluentUI.AspNetCore.Components and .Icons to 4.11.9
• Replace try/catch in IconResolver with IconInfo.TryGetInstance
• Delete FixedFluentCombobox component and switch references to FluentCombobox

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

File	Description
src/Aspire.Dashboard/Model/IconResolver.cs	Refactored to use TryGetInstance instead of catch‐all logic
src/Aspire.Dashboard/Components/Dialogs/FilterDialog.razor	Switched from FixedFluentCombobox to built-in FluentCombobox
src/Aspire.Dashboard/Components/Controls/FixedFluentCombobox.*	Removed temporary workaround component files
Directory.Packages.props	Bumped FluentUI package versions to 4.11.9

Comments suppressed due to low confidence (2)

src/Aspire.Dashboard/Model/IconResolver.cs:45

• [nitpick] The method takes both IconKey key (which includes DesiredIconSize) and a separate size parameter. Consider removing the redundant size argument and using key.DesiredIconSize to reduce duplication and potential mismatch.

private static bool TryGetIcon(IconKey key, IconSize size, [NotNullWhen(true)] out CustomIcon? icon)

src/Aspire.Dashboard/Model/IconResolver.cs:54

• Add a unit test for the failure path when TryGetInstance returns false to ensure coverage for missing icons and proper null handling.

return iconInfo.TryGetInstance(out icon);