UI nits from WinUI Controlsv2

In Terminal 1.13 we updated our version of WinUI to closer align with the Windows 11 styles. (in technical terms, we updated to ControlsV2). This had a variety of minor visual artifacts associated with it:

• #12395
  • upstream discussion: https://github.com/microsoft/microsoft-ui-xaml/issues/6684
  • potential workaround: https://github.com/microsoft/terminal/issues/9218
  • fixed in #12608
• New Tab icons aren't quite the right size: https://github.com/microsoft/terminal/issues/12395#issuecomment-1030874694
• #12398
  • Upstream: https://github.com/microsoft/microsoft-ui-xaml/issues/6685
• #12350
• #12388
  • Also includes:
  • #13285
  • #13068
  • #9775
  • #13428
• Colors are inconsistent between active tab, nav view, and tab content
  • 
  • But actually, that's just how it is in Xaml Controls Gallery too:
    
• #12574
• #13495

Relevant PRS:

• #12241
• #11720
• #12144
• #12287
• #12326
• #12374
• #12376
• #12381

Review the unchecked items in this tracking issue, especially the new tab icon sizing concern and #12388 with its remaining subitems. Follow the referenced issue comments and upstream WinUI discussions first, then use the linked related issues and PRs to determine which artifacts remain. Done means the remaining unchecked Controlsv2 visual issues are resolved or separately tracked.