Call a search activity when using KEYCODE_SEARCH

This change adds the ability to change the behavior
of the search key to open a search activity instead
of attempting to start the search activity of the
currently opened app. The new behavior remains the
same by default, but now it can be changed to
either do nothing or open a configured activity; in
this mode, if no activity has been configured,
the `ACTION_WEB_SEARCH` Intent will be launched.

Test: manual
Bug: 240865724
Signed-off-by: LiZhihong &lt;lizh52@lenovo.corp-partner.google.com&gt; DingYong <dingyong2@lenovo.corp-partner.google.com>
Change-Id: I3037d255b693ade3f45e170746e0c2b2de5db6fb