Isolate ListViewItem hover tests from the physical cursor

[Eales]

Fixes #12319

Proposed changes

• Replace physical cursor movement in the ListViewItem hover test with controlled
  accessibility bounds: an empty rectangle for outside and a rectangle covering the
  documented signed-16-bit virtual-screen coordinate range for inside. Neither value
  depends on the current monitor arrangement or DPI.
• Keep the real ListViewItem.IKeyboardToolTip.IsHoveredWithMouse implementation.
  Use the existing Moq protected-factory pattern to substitute only the accessibility
  bounds, with normal ListView behavior retained via CallBase.
• Restore the disabled virtual-mode/hovered case and remove its ActiveIssue marker.
  Keep the existing attached/detached and inside/outside cases. Verify that attached
  items consult the bounds and that the test does not create a native control handle.

Customer Impact

• Running this test no longer moves the user's cursor or races with mouse movement
  from another test or process.
• The previously disabled virtual-mode case runs again without requiring an
  interactive cursor-positioning step.

Regression?

• No product regression is being changed; this fixes existing test isolation.

Risk

• Low: one test file only, no product or public API changes, no new dependency,
  retries, skip conditions, or shared mutable state.
• The test still verifies the real hover decision, not a mocked hover result.
  Real native accessibility geometry remains outside this test's scope.

Test methodology

• Base: current main, 8efd9a920dba90722f8db1f7e943f74837d26579.
• Targeted hover theory: 5 passed, 0 failed, 0 skipped, with both pl-PL and
  en-US, including the restored virtual-mode case.
• Controlled mutation: temporarily force virtual-mode hover to return false. The
  restored positive case fails, and the bounds-read check also detects the bypass
  in the virtual-mode/outside case. Mutation removed before the final build/test.
• The original cursor-moving test was not executed on the active desktop. A local
  structural guard found its two Cursor.Position writes and passes after the fix;
  this is not a claim to reproduce the original intermittent CI failure.
• Broader class comparison: baseline 70 passed / 9 failed (hover excluded to
  avoid moving the cursor); patched 75 passed / 9 failed, with no exclusions or
  skips. The same nine unchanged ViewLargeIcon neighboring-rectangle cases fail
  before and after. Their layout assumptions are deliberately outside this PR.
• Release build: zero warnings/errors; git diff --check passes. The full repository
  suite was not run for this change.

Run the target from the built System.Windows.Forms.Tests executable with:

--filter-method System.Windows.Forms.Tests.ListViewItem_IKeyboardToolTipTests.ListViewItemKeyboardToolTip_InvokeIsHoveredWithMouse_ReturnsExpected

Test environment(s)

• Windows 11 25H2 x64, build 26200.9168.
• SDK 11.0.100-rc.1.26420.103; runtime 12.0.0-alpha.1.26458.117.
• Bounds rationale: Windows virtual-screen coordinate limits.

Microsoft Reviewers: Open in CodeFlow

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 37.24166%. Comparing base (8efd9a9) to head (4938908).

Additional details and impacted files

@@              Coverage Diff              @@
##                main      #15078   +/-   ##
=============================================
  Coverage   37.24166%   37.24166%           
=============================================
  Files            246         246           
  Lines           9774        9774           
  Branches        1029        1029           
=============================================
  Hits            3640        3640           
  Misses          5970        5970           
  Partials         164         164           

Flag	Coverage Δ
Debug	37.24166% <ø> (ø)
production	39.36526% <ø> (ø)
test	20.64923% <ø> (ø)
unit	39.36526% <ø> (ø)

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