Geo: Adds support for GeoJSON GeometryCollection

Closes #2796
[TEST] fix for wildcard_expansion REST tests

removed timeout from wait_for_green and set number of replicas to 0 so client tests can pass on single node.
[DOCS] document simple_query_string's `lenient` option
function_score: remove explanation of query score from functions

The score is explained already, it should not be again explained per function.

Also, remove explanation from parameter list of ScoreFunction#explainScore()
and leave only the score.

This also removes ExplainableSearchScript which is not used anywhere and
was the only reason to have the Explanation in the parameter anyway.

closes #7245
Docs: Document distance type and sort mode for many to many geo_points

closes #7280
Tests: tone down random compression tests

Closes #7314