For a long time runnable cpu load has been used in selecting task rq
when waking up tasks. Recent test has shown for test load with a large
quantity of short running tasks and almost full cpu utility, static load
is more helpful.

In our e2e tests, runnable load avg of java threads ranges from less than
10 to as large as 362, while these java threads are no different from
each other, and should be treated in the same way. After using static
load, qps imporvement has been seen in multiple test cases.

A new sched feature WA_STATIC_WEIGHT is introduced here to control. Echo
WA_STATIC_WEIGHT to /sys/kernel/debug/sched_features to turn static load
in wake_affine_weight on and NO_WA_STATIC_WEIGHT to turn it off. This
feature is kept off by default.

Test is done on the following hardware:

4 threads Intel(R) Xeon(R) Platinum 8269CY CPU @ 2.50GHz

In tests with 120 threads and sql loglevel configured to info:

	NO_WA_STATIC_WEIGHT     WA_STATIC_WEIGHT
	33170.63                34614.95 (+4.35%)

In tests with 160 threads and sql loglevel configured to info:

	NO_WA_STATIC_WEIGHT     WA_STATIC_WEIGHT
	35888.71                38247.20 (+6.57%)

In tests with 160 threads and sql loglevel configured to warn:

	NO_WA_STATIC_WEIGHT     WA_STATIC_WEIGHT
	39118.72                39698.72 (+1.48%)
Signed-off-by: NHuaixin Chang <changhuaixin@linux.alibaba.com>
Acked-by: NShanpei Chen <shanpeic@linux.alibaba.com>