Refine MaterialButton style and Don't capitalize buttons

1.Don't capitalize buttons
2.Simplify the style structure
3.Override Widget.MaterialComponents.Button
4.Override Widget.MaterialComponents.Button.OutlinedButton

Note:
Refer https://material.io/design/components/buttons.html

Test: atest DocumentsUIGoogleTests
      manual check the visual of Button

Fix: 123734206
Fix: 129101032

Change-Id: I3e302a257eee0400b0e95b40fd3b2e114def1609