Add an option to accept only JSON Objects

[dmikurube]

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[dmikurube]

It turned out that it wouldn't be easily realized because FilteringParserDelegate may not be able to raise an error for a JSON Object without a property matching with the JSON Pointer. (stop_on_invalid_record: true cannot be realized.)

See also:

• https://groups.google.com/g/jackson-user/c/bLZTjjjXZ28
• Test JsonPointerBasedFilter with sequence of JSONs #34

Because of this, we decided to release embulk-util-json:0.3.0 without this feature, and embulk-parser-json:0.11.1 without one-path parsing. embulk-parser-json:0.11.1 would be just changing Value to JsonValue.