from/to_base64 may return incorrect value when the value is null #4130
remove the duplicated base64 code
fix the base64 encoded string length is wrong， and this will cause the memory error
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.
LSAN detected errors have been fixed by a prior pathch (#3326), but
there are still some ASAN detected errors.
This patch try to fix these errors to make Doris BE more robustness.
And then we can add CI run in LSAN/ASAN mode to detect memory errors
as early as possible.
