MUI 6 Upgrade

[BirdMachine]

Upgrade to MUI 6 (We can save this for later too;)

• Breaking changes that stand out:
  • LoadingButton functionality's now baked into the standard Button
  • Typography component so longer uses the color prop, can use sx={{}} instead
    • It's not easy to immediately gleam where this approach is being used, might be be gone after forum upgrades are finished
  • IE11/Trident Support ends
  • The way the Grid layouts are calculated is changing

Should be addressed after the Form upgrades, not before/during (though helps to keep in mind)