This CL mainly includes:
- add some methods to get thread's stats from Linux's system file in
env.
- support get thread's stats by http method.
- register page handle in BE to show thread's stats to help developer
position some thread relate problem.
The code submitted later will use this utility class.
Currently only factory methods for various file types are provided.
In the future, tool methods that are common to all Env types can
be added here.
