enhancement: RateLimitFilter - Provides an exact rate limiting mechanism

[Chenjp]

smaller PR from #767 .
If you need exact rate limiting and can accept a small decrease in efficiency, ExactRateLimiter may be an alternative option.

[Chenjp]

minimize API change.

[markt-asf]

You can't remove methods from the RateLimiter interface as it been included in a stable release.

[Chenjp]

You can't remove methods from the RateLimiter interface as it been included in a stable release.

Updated

[markt-asf]

The PR makes a very large number of unnecessary changes which makes it extremely hard to review. I have already spend multiple hours just reviewing the refactoring of TimeBucketCounter.

I have yet to decide whether I will proceed with applying those changes as a first step towards to implementing the changes proposed in this PR or whether I'll opt to close this PR and request a series of smaller PRs where each PR addresses a single concern and, potentially, breaks larger, related changes into a series of smaller, reviewable commits.

[markt-asf]

It turns out the TimeBucketCounter was by far the most complex. Once that was reviewed, the rest followed quite quickly. I'm leaving this PR open as there are some changes - particularly the change to eviction - that might need to be added.

[markt-asf]

Closing as I believe all points raised in this PR have now been addressed.