Ensure Suggestions List is shown to Accessibility users on Tablets.

Accessibility users who interact with the Omnibox on Large Form
Factor devices using Hardware Keyboard may not be offered a list
of suggestions until they - somehow - explicitly touch or click the
Omnibox. This is because the Accessibility suite activates widgets
using performClick, rather than emitting touch events.

This change decouples the initial (touch/click) activation from
subsequent (tap/touch) activations, allowing the Accessibility
focus event to be intercepted and propagated in order to present the
suggestions list in the event Omnibox was shown pre-focused.

The Focus events are emitted _only once_ per activation session.
- if the focus is requested by the user via touch/click/accessibility
  only `onFocusByTouch()` event is emitted.
- if the focus is requested programmatically, bypassing the
  conventional flow (touch/click/accessibility focus), only
  `onTouchAfterFocus()` event is emitted.

Note this change fixes the emitted Omnibox Events:
- If Omnibox was activated with click/touch/..., only `FOCUS_BY_TOUCH`
  activation event is recorded
- Otherwise, if Omnibox was pre-activated, only `TOUCH_AFTER_FOCUS`
  activation event is recorded
- `TOUCH_AFTER_FOCUS` events are emitted only once per Omnibox session
  (i.e. subsequent Omnibox touches will not emit events).

Change-Id: Idd891f0424a0b46182e534487b65b8120c306fdd
Fixed: b:352127629
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5690372
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Commit-Queue: Tomasz Wiszkowski <ender@google.com>
Reviewed-by: Patrick Noland <pnoland@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1325727}