[Tracking] Important manually review work for DarkMode for Preview 7

[KlausLoeffelmann]

• [ ] Make ToolStripDarkModeRenderer sealed (https://github.com/dotnet/winforms/pull/13360#discussion_r2150547419)
• [ ] Make GetDarkModeColorMode more efficient https://github.com/dotnet/winforms/pull/13360#discussion_r2150561605
• [ ] Follow-up on GraphicsInternal issue in the ToolStripRenderer (https://github.com/dotnet/winforms/pull/13360#discussion_r2150563626) also see (https://github.com/dotnet/winforms/pull/13360#discussion_r2150533337)
• [ ] Followup on Windows version in DarkMode renderer https://github.com/dotnet/winforms/pull/13360#discussion_r2150538324
• [ ] Making the DarkModeButtonColors sealed (https://github.com/dotnet/winforms/pull/13408#discussion_r2150786880)
• [ ] Make the rules for XML comments more precicise for refactoring purposes. https://github.com/dotnet/winforms/pull/13408#discussion_r2150779536
• [ ] The Button renderer docs are very confusing, and I want to sit with Andy to see what we can do for it. (https://github.com/dotnet/winforms/pull/13408#discussion_r2150771055 - also @adegeo FYI.)
• [ ] Extend on comment for purpose of code change. (https://github.com/dotnet/winforms/pull/13408#discussion_r2150768798)
• [ ] Weird comment, needs to be addressed. https://github.com/dotnet/winforms/pull/13408#discussion_r2150758161
• [ ] Redundant comment. https://github.com/dotnet/winforms/pull/13408#discussion_r2150767391
• Make sure to restore any deliberately Graphics mode back to normal (several spots:)
  • [ ] https://github.com/dotnet/winforms/pull/13408#discussion_r2150762833
  • [ ] https://github.com/dotnet/winforms/pull/13408#discussion_r2150762168