Fix version checking with mixed state

[JamesNK]

Description

How the bug occurs:

1. You're running pre-release.
2. Version checker runs and sees a newer version. Saved to state.
3. Within the version check interval (2 days) you switch the app to release.
4. Version checker uses save state on startup. Release app prompts for newer pre-release version.

Fix is to unify logic for getting new version through PackageUpdateHelpers.GetNewerVersion.

(I don't think a backport is required. This is a niche and easily ignorable scenario)

Fixes #10749

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 fixes a bug in version checking logic where switching between pre-release and release versions within the check interval could cause inappropriate version notifications. The fix unifies the version comparison logic to properly handle mixed pre-release and stable version states.

• Unified version checking logic to consider both fetched and stored versions together
• Added dependency injection for package version provider to improve testability
• Enhanced test coverage for mixed pre-release/stable version scenarios

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Shared/PackageUpdateHelpers.cs	Modified GetNewerVersion to accept and process stored version alongside fetched packages
src/Aspire.Hosting/VersionChecking/VersionCheckService.cs	Refactored to use injected package version provider and unified version checking logic
src/Aspire.Hosting/VersionChecking/IPackageVersionProvider.cs	Added new interface for package version retrieval
src/Aspire.Hosting/VersionChecking/PackageVersionProvider.cs	Implemented concrete package version provider
src/Aspire.Hosting/DistributedApplicationBuilder.cs	Registered new package version provider service
tests/Aspire.Hosting.Tests/VersionChecking/VersionCheckServiceTests.cs	Added comprehensive tests for mixed version scenarios and test infrastructure