Dump accessibility event and node when tag is loggable

Let accessibility cache to dump events and nodes info only when
log.tag property has been set up in a debuggable build.

When analyzing we care about events before diving into details.
Using separate log level to decrease interfere and to lower the
performance impact.

- To debugging Cache and event set log.tag.AccessibilityCache property
  to DEBUG
- To dump node as well when get/add to Cache set
  log.tag.AccessibilityCache property to VERBOSE
- To dump additional debug info for NodeInfo/Event set corresponding
  log.tag.AccessibilityNodeInfo/log.tag.AccessibilityEvent property set
  to DEBUG.

Bug: 117150182
Test: `setprop log.tag.AccessibilityCache D` and
      enable talkback to use and check logcat manually
Test: `setprop log.tag.AccessibilityCache V` and
      enable talkback to use and check logcat manually

Change-Id: I433e21ffd21d4125caf938bc8271135bcefd66c3