Adding contrast borders for a DataGridViewCheckBoxCell in Win11.

[NikitaSemenovAkvelon]

Fixes #6657

Proposed changes

• Added RoundedRectangle class which encapsulates the painting logic for a rounded rectangle.
• Used RoundedRectangle inside DataGridViewCheckBoxCellRenderer for Win11.

Customer Impact

• A user can see CheckBox inside DataGridView more clearly.

Regression?

• No

Risk

• Minimal

Screenshots

Before

After

Test methodology

• Manually
• AI

Accessibility testing

• AI

Test environment(s)

• 7.0.100-preview.5.22307.18

Microsoft Reviewers: Open in CodeFlow