Wylie Conlon a86c8dce70 Clarify field data cache behavior in docs (#64375)
* Clarify that field data cache includes global ordinals
* Describe that the cache should be cleared once the limit is reached
* Clarify that the `_id` field does not supported aggregations anymore
* Fold the `fielddata` mapping parameter page into the `text field docs
* Improve cross-linking
2020-11-20 13:59:52 -08:00
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