[FEATURE] Support Json related functions

[xinyual]

Is your feature request related to a problem?
In spark we have json related functions https://github.com/opensearch-project/opensearch-spark/blob/main/docs/ppl-lang/functions/ppl-json.md, we also want it in opensearch PPL.

[xinyual]

But I find the performance of some spark functions are wired. We need to discuss its performance. I write my expectation for this function

Functions	json path input ? ('$.f1.f2')	support regex input? ('$.f1[*].f2')	perform when json path point to null	perform when father path point to null
json_extract	Y	Y	return null	return null
json_set	Y	Y	do insert anyway	do nothing
json_delete	Y	Y	do nothing	do nothing
json_append	Y	Y	do nothing	do nothing
json_extend	Y	Y	do nothing	do nothing

And here is the spark's performance

Functions	json path input ? ('$.f1.f2')	support regex input? ('$.f1[*].f2')	perform when json path point to null	perform when father path point to null
json_extract	Y	Y	return null	return null
json_set	N	N	insert anyway	insert anyway
json_delete	N	N	do nothing	do nothing
json_append	N	N	the value are added to the root of the json tree	the value are added to the root of the json tree
json_extend	N	N	the value are added to the root of the json tree	the value are added to the root of the json tree

And here are the functions in calcite

Functions	corresponding calcite implementation	json path input ? ('$.f1.f2')	support regex input? ('$.f1[*].f2')	perform when json path point to null	perform when father path point to null
json_extract	json_value/json_query	Y	N. json_value return scalar while json_query return object/array. We need a combination	return null	return null
json_set	Json_set	Y	N. Calcite use JsonPath.isPathDefinite	do insert anyway	do nothing
json_delete	json_remove	Y	N. Calcite use JsonPath.isPathDefinite	do nothing	do nothing
json_append	json_insert	Y	N. Calcite use JsonPath.isPathDefinite	do nothing	do nothing
json_extend	/	/	/	/	/

BTW, for json_append and json_extend, the only difference is when the target object the json path pointed is an array and candidate input is also an array, append would directly add it as [a, b, [candidate1, candidate2]] while extend would [a, b, candidate, candidate..] can we implement only one command? Looks the calcite only support json_append using sqlLibraryOperators.JSON_INSERT

[xinyual]

cc. @LantaoJin @penghuo

[penghuo]

json_extract

in opensearch-spark, current json_extract return string, the expectation is ARRAY or PPL scaler data type?

[xinyual]

Will align with splunk implementation. https://docs.splunk.com/Documentation/SCS/current/SearchReference/JSONFunctions#json_extract.28.26lt.3Bjson.26gt.3B.2C_.26lt.3Bpaths.26gt.3B.29