Add showSoftKeyboard method to Utils, and use it where necessary.

- When the Search field is clicked, or when it gains focus
- When the Find-in-page field comes into view
- When the "other" edit summary comes into view

This also fixes the behavior of the Nav menu when clicking/focusing on the
Search field.

Bug: 68682

Change-Id: I3290f8921c02b29844b480995dc8220e746ba644