Improve performance of util.CurrentTimeMillis() adaptively under different load conditions

[sczyh30]

Issue Description

Type: feature request

Describe what feature you want

Improve performance (CPU footprint) of util.CurrentTimeMillis() adaptively under different load conditions. Current design of TimeUtil may cost much more than users think in mind in idle systems.

Additional context

Refer alibaba/Sentinel#1746

[cbl315]

Do we have a bench test result now for util.CurrentTimeMillis()?
It's better to have a base before improve it I think.

[cbl315]

/assign

[sczyh30]

The UseCachedTime feature will be disabled by default in the next version, according to the discussions in #441, #442