[HDPI] CheckBox doesn't respect system font scaling

* .NET Core Version: all up to latest (5.0.5)

* Have you experienced this same bug with .NET Framework?: No because .NET Framework doesn't respect system font scaling at all.

**Problem description:**
Probably all CheckBox stuff (`CheckBox`, `TreeView` with checkboxes, `CheckBoxRenderer` e.t.c.) doesn't respect system font scaling for check box image:
P.s. TreeView plus/minus signs also not increasing.

**Expected behavior:**
I think image must scale with Font too (especially because of font scaling is used by default). It's just pointless to enlarge the text, but not enlarge the checkbox image. But if it's by design, feel free to close this issue.

**Minimal repro:**
Any WinForm app with `HighDpiMode.SystemAware` + `CheckBox` and increased System font.