fix(Button): Add new color scheme tokens & update iconOnly button styles for Teams theme

[codepretty]

Support background5 and backgroundHover2 default design token in Teams themes

Updated iconOnly buttons to use backgroundHover2 for the correct hover background in Teams high contrast theme

1. Icons in buttons should not be filled on focus, only on hover
   Before
   

After

2. Icon only text button should have a yellow background and black text color on hover in Teams high contrast
   Before
   

After

Example using the new background5 token for a background in all Teams themes

[DustyTheBot]

Perf comparison

Status	Scenario	Fluent TPI	Fabric TPI	Ratio	Iterations	Ticks
🔧	Avatar.Fluent	0.65	0.42	1.55:1	2000	1304
🔧	Button.Fluent	1.48	0.2	7.4:1	1000	1475
🔧	Checkbox.Fluent	1.68	0.37	4.54:1	1000	1675
🔧	Dialog.Fluent	0.39	0.21	1.86:1	5000	1962
🔧	Dropdown.Fluent	3.7	0.41	9.02:1	1000	3703
🔧	Icon.Fluent	0.28	0.04	7:1	5000	1422
🔧	Image.Fluent	0.11	0.07	1.57:1	5000	558
🔧	Slider.Fluent	1.96	0.3	6.53:1	1000	1961
🦄	Text.Fluent	0.05	0.17	0.29:1	5000	254
🦄	Tooltip.Fluent	0.44	19.37	0.02:1	5000	2194

🔧 Needs work     🎯 On target     🦄 Amazing

Generated by 🚫 dangerJS

[mnajdova]

LGTM, make sure the screener differences are accepted