[profiler] Report some metrics as quantiles #7557

Many performance metrics use count or max, but they would be more useful when collected as histograms and reported in the profiler as a selected set of quantiles. We can probably reuse the existing ExponentialHistogram for this purpose, perhaps after making it configurable, or we could define a smaller histogram object.

Example: number of iterations needed to settle recursion, cache miss size, cache miss duration distribution, step duration, wait duration, batch size, etc.