This commit adds a new API to allow scripts to say whether they need scores.
In practice, only the `expression` script engine makes use of it correctly,
other engines just return `true` since they can't predict whether they'll
need scores. This should make scripted aggregations and `function_query`
faster as we'll now be able to pass needsScores=false to Query.createWeight.
Modified ScriptEngineService to pass in a CompiledScript object
with newly added name and type member variables.
This can in turn be used to give better scripting error messages
with the type of script used and the name of the script.
Required slight modifications to the caching mechanism.
Note that this does not enforce good behavior in that plugins will
have to write exceptions that also output the name of the script
in order to be effective. There was no way to wrap the script
methods in a try/catch block properly further up the chain because
many have script-like objects passed back that can be run at a
later time.
closes#6653closes#11449
