Allow JSON Document caching

[wilsonge]

Summary of Changes

Allows the caching of JSON Documents if something requests it. In webservice custom applications (e.g. the Joomla Downloads Site) this is an important optimisation (and will be required in J4 whether accepted in j3 or not)

In order to keep behaviour I've ensured that both com_config and com_finder do not cache the response under any circumstance

Testing Instructions

N/A - There's no change in behaviour for core components. Ensure finder works the same before and after patch

Documentation Changes Required

JSON Responses can be cached

[alikon]

I have tested this item ✅ successfully on 9f02876

---

_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/27161.}

[HLeithner]

Thanks