Bug 443572 - [Performance] Option to report UI delay as error

Introduced two separate event duration thresholds, one for logging as
warning and another for logging as error. The second threshold also has
an effect of capturing stack traces of all threads.

Removed sampling interval and initial delay preferences to simplify the
preference page.

Improved formatting of delay duration.

Added @noextend to StackSample and UiFreezeEvent classes.

Change-Id: Ic525e7a666f5fcdfac411e00a70ee9a99eca1fc6
Signed-off-by: Sergey Prigogin <eclipse.sprigogin@gmail.com>