Replace multi_json and oj gems with standard Ruby json gem

[larouxn]

Description

Proposing we remove the multi_json and oj gems in favour of the standard Ruby json gem as it's now as fast or faster in the majority of cases compared to oj. Additionally allows us to simplify code quite a bit too. ✨

Related efforts

• Change the default serializer to the json gem for 4.0.0-beta.5 opensearch-project/opensearch-ruby#290
• Remove oj and its initializer and add json to the Gemfile mastodon/mastodon#37752

Implementation

Generally it's a pretty simple swap and cleanup. That said, the one quirk comes from the fact that oj could apparently handle non-finite doubles such as infinity. As the Standard JSON (RFC 8259) does not support non-finite doubles such as NaN, Infinity, and -Infinity as numeric values, the JSON gem can raise a JSON::GeneratorError when passed such values for generation. Thus, I'm proposing we use string representation + type for such values. Open to opinions.

Probably worth reviewing with whitespace disabled re: the indentation changes in spec/api_spec.rb. Link below.

https://github.com/ruby-rdf/json-ld/pull/64/changes?w=1

Notes

Apparently v1.20.0 of multi_json dropped support for ok_json. 🤷‍♂️ 🔥

[CLAassistant]

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[larouxn]

Note that we either need to merge this or alternatively a smaller PR that just drops ok_json support since v1.20.0 of multi_json dropped support for ok_json which thus leads to CI here being broken.

PR to drop no-longer-supported serializers:

• Drop support for ok_json and json_pure as multi_json has done #66