[Settingslib] Fix TopIntroPreference and IntroPreference.

1. Replace MaterialButton with LinearLayout (with image and text view) for better alignment.
2. Set default value of `isCollapsable` of IntroPreference and TopIntroPreference to `false`.
3. Let the icon not focusable when setting the accessibility

Bug: 405308129
Test: manual + presubmit
Flag: EXEMPT resource update only

Change-Id: I3ec357210f1e5e135fc4a1b5f3b8f8900c175af7