perf report: Add option to specify time window of interest

Add option to allow user to control analysis window. e.g., collect data
for time window and analyze a segment of interest within that window.

Signed-off-by: David Ahern <dsahern@gmail.com>
perf script: Add options to show only userspace or kernel functions

Signed-off-by: David Ahern <dsahern@gmail.com>
perf sched timehist: Add options to show only userspace or kernel functions

Signed-off-by: David Ahern <dsahern@gmail.com>