Bug fix: custom query in Count doesn't return correct result

[bowenxia]

What changed?
CountQuery used to return an empty string when there are errors in the query and then log the error. Changed it to return error instead of log.
Also updated tests in PinotQueryValidator and pinot_visibility_store

Why?
When a custom query has something like "CustomKeywordField = missing", the list APIs will return errors because "xxx = missing" is only supported for system keys. (Same for ES) In the current situation, the custom query in count return an empty string and thus Cadence will have a wrong result. This needs to be changed.

How did you test it?
unit test

Potential risks

Release notes

Documentation Changes

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.

Project coverage is 72.76%. Comparing base (4a51fb4) to head (b8f662f).

Additional details and impacted files

Files	Coverage Δ
common/persistence/pinot/pinot_visibility_store.go	93.47% <88.88%> (+0.31%)	⬆️

... and 7 files with indirect coverage changes

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