[DocsUI M3] Restyle dialog buttons

* use filled button style for primary button in dialogs
* use outlined button style for secondary button in dialogs
* use text button style for neutral button in dialogs

Check the attached bug for the demo.

Bug: 404351298
Test: m DocumentsUIGoogle && manual inspection
Flag: com.android.documentsui.flags.use_material3
Change-Id: I9c418bb0d82dfe7475e482074884f0658f2c16d1