Consolidate JSON, JSONParseResults and JSONParser into JSON

[madmiraal]

Following #44574 (comment).

Supersedes #44574
Part of #16863

Removes JSONParser and JSONParseResults.

Includes renaming:

• JSON::parse_string() to parse()
• JSON::decode_data() to stringify()

Note 1: stringify() returns the String instead of Error::Ok.
Note 2: Adds a to_json_string() method to Variant for use within the engine.

Edit: JSONParser has been renamed to JSON following PR Review meeting (comment)

[dalexeev]

Maybe rename the JSONParser to JSON?

In my opinion, the JSON singleton was more convenient, now you need to create a JSONParser instance every time.

[Xrayez]

In my opinion, the singleton was more convenient, now you need to create a JSONParser instance every time.

I really think that we need support for defining static functions for scripting as provided by built-in classes, see my comments on this at godotengine/godot-proposals#1101 (comment) which also happens to mention JSON, this would solve the convenience issue...

[dalexeev]

On the other hand, a new JSONParseResult instance was already created every time JSON.parse() was called. So the difference is not very big, but it is consistent with XMLParser.

[madmiraal]

Rebased following merge of #44859 and #44911.

[madmiraal]

Rebased following merge of #44989.

[madmiraal]

Rebased following merge of #45737.

[madmiraal]

Rebased following merge of #46200.

[madmiraal]

Rebased following merge of #46551.

[madmiraal]

Rebased following merge of #46713 and #46728.

[madmiraal]

Rebased following merge of #40804.

[madmiraal]

Rebased following merge of #48159, #48239, #47386 and #47974.

[akien-mga]

We discussed this in a PR review meeting today and approved consolidating those APIs in one place (again, I remember this PR followed a discussion in another meeting). The only change we'd suggest is that since the new JSONParser class is also used for writing (stringify), it should maybe renamed to just JSON. The other *Parser classes we have like VariantParser and XMLParser only do parsing, not writing.

[madmiraal]

Renamed JSONParser to JSON.

[akien-mga]

Thanks!

[Faless]

I don't understand why the engine exposed JSON::stringify is no longer static.
Having to write in engine every time:

JSON json;
json.stringify(...);

is quite awful.

[madmiraal]

@Faless The PR includes the addition of a to_json_string() method to Variant for use within the engine.

Note 2: Adds a to_json_string() method to Variant for use within the engine.

godot/core/variant/variant.cpp

Lines 1842 to 1845 in 56d7126

	String Variant::to_json_string() const {
	JSON json;
	return json.stringify(*this);
	}

Note: If the variable is not a Variant but can be converted to one there is also this option: Variant(my_variable).to_json_string() for example:

godot/modules/gdscript/language_server/gdscript_language_protocol.cpp

Lines 281 to 282 in 56d7126

	Dictionary message = make_notification(p_method, p_params);
	String msg = Variant(message).to_json_string();

[Faless]

@madmiraal thanks for the clarification. I had totally missed it. My apologies.