WI01087563 Fix high DPI anchor layout regression

[FahmiFuzi]

Fixes WI01087563

Proposed changes

• Restore cached anchor bounds for high-DPI stretch refresh cases where the proposed bounds are wider/taller than the display area.
• Add regression coverage for nested anchored controls at high DPI.
• Keep the fix scoped to anchor layout compatibility behavior.

Customer Impact

• Reduces .NET 10 WinForms layout regressions where anchored child controls are resized outside their parent by DPI/runtime rounding.
• Avoids requiring downstream products to patch individual forms and controls for framework-level anchor behavior.

Regression?

• Yes. .NET 10 behavior diverged from the previous .NET 8 / .NET Framework layout behavior under high DPI anchoring.

Risk

• Moderate: layout code is shared, but the change is guarded by cached bounds and display-area checks so it only applies when the current stretch refresh would produce bounds beyond the available display area while the cached bounds still fit.

Screenshots

N/A - layout regression is covered by automated bounds assertions.

Test methodology

• ./eng/common/dotnet.cmd test src/System.Windows.Forms.Legacy/System.Windows.Forms.Legacy.Tests/System.Windows.Forms.Legacy.Tests.csproj --filter "FullyQualifiedName~AnchorLayoutHighDpiRegressionTests" --logger "console%3Bverbosity=minimal"
• Verified the same repro fails on unpatched origin/master and passes with this patch.
• Validated downstream CargoWise Group 9 tests using this patched runtime.

Accessibility testing

N/A - no new UI or accessibility surface; this restores layout bounds behavior.

Test environment(s)

• Windows
• .NET 10 WinForms build/test environment
• High-DPI regression test coverage