Agg test coverage for unmapped, scripting, supported-types

[polyfractal]

Before merging the VS refactoring work, we'd like to make sure all the converted aggs have tests for unmapped, scripting and "supported type" tests to avoid accidentally changing any behavior. These corner cases have some nuanced behavior, and are not well tested in master today.

I've randomly divided up the set of aggs below. Many are already tested (either previously, or added for the VS refactoring), so just verify and check off. If they are missing please work on a PR against master and the feature branch.

@polyfractal:

• Histo field / percentiles
• Value Count Add scripting, supported-type tests to ValueCount #53500
• Terms Add scripting and missing tests for Terms agg #54128
• Cardinality
• Boxplot Add scripting, unmapped, supported-type tests to Boxplot #53435
• Geo Tile Grid
• Percentiles
• Rare Terms
• Range

@csoulios:

• Average (Migrate tests from AvgIT integration test to AvgAggregatorTests #44076, Add supported-type tests to Average aggregation #54011)
• Min (Migrate MinAggregator integration tests to AggregatorTestCase #50053, Add supported type tests to min aggregation #54021)
• Median (Add tests to MedianAbsoluteDeviationAggregator #54884)
• Extended Stats
• Significant Terms
• Geo Hash Grid
• Geo Bounds
• Percentile Rank

@andyb-elastic

• Sum add tests to SumAggregatorTests #53568
• Date Range value type, unmapped field, scripting tests for date range agg #55502
• Missing add tests for missing aggregation #53214 migrate tests from MissingIT to MissingAggregatorTests #53448
• Histogram
• String Stats value type, scripting, missing param, yaml tests for string stats agg #54033
• Max supported field type tests for max agg #53701
• Geo Centroid
• Stats value type, unmapped fields, scripting, missing param tests for stats agg #53768

New, whoever gets here first:

• Date Histogram

[elasticmachine]

Pinging @elastic/es-analytics-geo (:Analytics/Aggregations)