fix: Adds a new config check to insert SPQ Processor

[AlanConfluent]

Description

Replaces the check for ksql.query.push.scalable.enabled with ksql.query.push.scalable.registry.installed to insert the streams Processor for Scalable Push Queries. The idea behind this is that we want the user to be able to enable SPQs using the config ksql.query.push.scalable.enabled per request or in the CLI and control the registry installation separately.

Also, ups the ProcessingQueue limit to 1000 to allow for larger bursts.

Testing done

Verified it works as intended.

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")

[guozhangwang]

I'm +1 to the idea of making this enabling at the per-query/request level.

Just clarifying, at the per-request level this config is still turned off by default or not?

[agavra]

thanks! as discussed offline, I'm +1

[AlanConfluent]

I'm +1 to the idea of making this enabling at the per-query/request level.

Just clarifying, at the per-request level this config is still turned off by default or not?

It is off by default, but will be possible to enable per query, in which case it will still only use SPQs if they are appropriate.