* Merge instrument cache to inserter
The current pipeline resolution path will only add the resolved
aggregators to the pipeline when it creates one (cache miss). It will
not add it if there is a cache hit. This means (since we cache
instruments at the meter level, not the pipeline level) the first reader
in a multiple-reader setup is the only one that will collect data for
that aggregator. All other readers will have a cache hit and nothing is
added to the pipeline. This is causing #3720.
This resolves#3720 by moving the instrument caching into the inserter.
This means aggregators are cached at the reader level, not the meter.
* Rename aggCV to aggVal
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Co-authored-by: Chester Cheung <cheung.zhy.csu@gmail.com>
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