Lucene index: Index definitions implications of isRegexp

It would be good to put a sentence in the documentation (in the `isRegexp` section of  [1]) citing if there are any adverse implications of using `isRegexp` in conjunction with options like `property=true`, `facets=true`, or other configs.

The common use of `isRegexp` is a way to index many properties, variable properties (variable in number). Any implications (or lack thereof) for this "broad brushed" approach with should be articulated to guide developers to use `isRegexp` in a responsible manner.

[1] https://jackrabbit.apache.org/oak/docs/query/lucene.html#property-definitions