Change QueryTemplateParser to use script naming convention

[colings86]

At the moment the QueryTemplateParser uses query, file and id for inline, file and indexed scripts respectively. Since the naming convention for scripts is now script, script_file and script_id (enforced by using the ScriptParameterParser) we should change this API to follow the same convention. We may want to keep query as an option for inline scripts as it makes sense in this context but we should support script too. file and id should be replaced with script_file and script_id.

Original comment in: https://github.com/elasticsearch/elasticsearch/pull/9992/files#r25855691

[clintongormley]

file and id should be replaced with script_file and script_id.

Or query_file and query_id? Not sure it is obvious to users that "templates" are a form of scripting.

Also, we can leave file and id and just mark them as deprecated, no?

[colings86]

@clintongormley yep, good point. It should be noted that ScriptParameterParser can still be used for this since it accepts arbitrary prefixes as well as the default script prefix. As for deprecation, yes we can but as will the script options we could also deprecate in 1.5 and remove in 2.0?

[javanna]

I think we should come up with a Script construct that holds all the relevant parsing code, which needs to be streamlined whenever we support scripts in the codebase. Script would then hold 'lang', 'type', the script itself etc. and could be passed as a single argument to ScriptService etc. instead of the different arguments that we currently have.

[uboness]

+1 on the Script construct... it should also implement ToXContent.

[clintongormley]

Closed in favour of #11164