build(deps): bump ReactiveUI.Binding to 8.7.0 and ReactiveUI.Primitives to 8.4.0

[glennawatson]

Summary

ReactiveUI now builds against ReactiveUI.Binding 8.7.0 and ReactiveUI.Primitives 8.4.0.

• BindingVersion in Directory.Packages.props is now 8.7.0, and PrimitivesVersion is now 8.4.0.
• The WPF, WinForms and MAUI binding packages now write through each platform's Primitives sequencer, which ReactiveUI's platform packages pick up through this bump.

Why

ReactiveUI.Avalonia and ReactiveUI.Uno move to the new ReactiveUI.Binding.Avalonia and ReactiveUI.Binding.Uno packages. Those packages need ReactiveUI.Binding 8.7.0 and ReactiveUI.Primitives 8.4.0. ReactiveUI has to reference the same versions and be released first, so the platform packages do not pull ReactiveUI onto versions it was never built against.

Breaking changes

None. Binding 8.7.0 and Primitives 8.4.0 are additive releases.

How this was verified

Built the whole solution and ran the test projects CI runs on Linux. The Windows-only test projects run in CI.

Notes for the reviewer

A version bump only.

Checklist

• I have read the Contribute guide
• The PR title follows Conventional Commits
• Tests cover this change, or the summary says why they do not
• New or changed public API has XML documentation

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.69%. Comparing base (3a1d270) to head (199def4).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4529   +/-   ##
=======================================
  Coverage   93.69%   93.69%           
=======================================
  Files         175      175           
  Lines        6231     6231           
  Branches      743      743           
=======================================
  Hits         5838     5838           
  Misses        392      392           
  Partials        1        1           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.