Unhighlighting the ToolStripMenuItem when it is in the drop-down menu

[LeafShi1]

Fixes #11550

Proposed changes

• Unhighlighting the ToolStripMenuItem when it is in the drop-down menu
• Add third level menu item in ToolStripTests.cs of the test project WinformsControlsTest

Customer Impact

• The color contrast of the toolStripMenuItem's indeterminate state icon is sufficient, regardless of whether the selected state is enabled or disabled.

Regression?

• Yes

Risk

• Minimal

Screenshots

Before

toolStripMenuItem is highlighted in unfocused state when its check property is enabled, this causes the color contrast of indeterminate state icon for toolStripMenuItem is less than 3:1.

After

Unhighlighting the ToolStripMenuItem when it is in the drop-down menu

Test methodology

• Manually

Test environment(s)

• .net 9.0.0-preview.6.24318.5

Microsoft Reviewers: Open in CodeFlow

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 74.44438%. Comparing base (566bec4) to head (ca33113). Report is 18 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #11557 +/- ## =================================================== - Coverage 74.48439% 74.44438% -0.04002% =================================================== Files 3039 3039 Lines 629066 629067 +1 Branches 46834 46834 =================================================== - Hits 468556 468305 -251 - Misses 157154 157404 +250 - Partials 3356 3358 +2 ``` | [Flag](https://app.codecov.io/gh/dotnet/winforms/pull/11557/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | Coverage Δ | | |---|---|---| | [Debug](https://app.codecov.io/gh/dotnet/winforms/pull/11557/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | `74.44438% <50.00000%> (-0.04002%)` | :arrow_down: | | [integration](https://app.codecov.io/gh/dotnet/winforms/pull/11557/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | `17.89617% <0.00000%> (-0.08232%)` | :arrow_down: | | [production](https://app.codecov.io/gh/dotnet/winforms/pull/11557/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | `47.25975% <50.00000%> (-0.08857%)` | :arrow_down: | | [test](https://app.codecov.io/gh/dotnet/winforms/pull/11557/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | `96.97153% <ø> (+0.00029%)` | :arrow_up: | | [unit](https://app.codecov.io/gh/dotnet/winforms/pull/11557/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet) | `44.33480% <50.00000%> (-0.00331%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dotnet#carryforward-flags-in-the-pull-request-comment) to find out more.