Validate parameters of native sig score scripts so that we know which…

… ones are not set.

[docs] Add missing article

[docs] Add missing article to zen.asciidoc

Fix index name equality check in RoutingNodes

This commit fixes an index name equality check in RoutingNodes. Namely,
the check was comparing an instance of Index to an instance of
String. Instead, the index name should be obtained from the Index
instance to be compared to the instance of String.

Closes elastic#17982

[TEST] fix version for bwc 2.2 test

Changed JAVA_OPTS to ES_JAVA_OPTS in plugin docs

Document task id's as string in the rest spec

In cat.snapshots, repository is required

Closes elastic#17216

In cat.snapshots, repository is required

Closes elastic#17216

Add missing index name to indexing slow log

This was lost in a previous refactoring moving away from AbstractIndexShardComponent
which automatically adds the hostname and the shard ID to the logger prefix. This commit
brings back this property.

Relates to elastic#17025
Backport of elastic#17026

release [1.7.5]