Add `:immutable` parameter to `from-json`

[lizmat]

Add :immutable parameter to from-json and some other optimizations

• abstract die-ing logic into separate subs to reduce the binary size of the processing units, making it likelier they would be inlined if no errors are encountered
• abstracted parsing "true", "false", "null" into subs so that they can be used in ternaries, they should easily be inlined if so needed.
• converted parse-thing to just ternaries for better readability
• created "immutable" versions of parse-thing, parse-obj and parse-array to contain optimized versions of parsing logic for immutable results.
• makes "normal" parsing about 1% faster (on a 6MB JSON file with all of the Raku ecosystem's current and past JSON files)
• "immutable" parsing is about 5% faster, and creates about 9% smaller memory footprint (for that 6MB JSON file).
• in the case of immutable parsing, empty arrays and hashes are actually bound to a singleton empty List and Map
• added documentation for the from-json :immutable feature
• Upped the version for convenience and to more easily allow comparisons to be made locally

[lizmat]

Any progress? Anything wrong? The suspense is killing me! :-)

[lizmat]

@timo Hope you're holding up on your $work.

If it is becoming too much for you to maintain this module, please let me know. I could well take over maintenance of this module, as am pretty aware of its inner workings :-)

[lizmat]

Or we could move it to community-modules?

[lizmat]

It's been over 3 months now, and I'm getting tired of waiting. And seriously considering forking this module in raku-community-modules and releasing it with a higher version number.

Please let me know if there is anything that needs to be done to this PR to make it acceptable.