refactor: converted PactDslJsonBody to Kotlin #1667

Job	Run time
supported_jdks (core, 8)	2m 54s
supported_jdks (core, 9)	3m 21s
supported_jdks (core, 11)	2m 40s
supported_jdks (consumer, 8)	3m 51s
supported_jdks (consumer, 9)	5m 33s
supported_jdks (consumer, 11)	4m 17s
supported_jdks (provider, 8)	5m 29s
supported_jdks (provider, 9)	6m 15s
supported_jdks (provider, 11)	5m 50s
supported_jdks (pact-specification-test, 8)	1m 54s
supported_jdks (pact-specification-test, 9)	2m 33s
supported_jdks (pact-specification-test, 11)	2m 8s
latest_jdk (ubuntu-latest, core)	3m 4s
latest_jdk (ubuntu-latest, consumer)	4m 7s
latest_jdk (ubuntu-latest, provider)	5m 58s
latest_jdk (ubuntu-latest, pact-specification-test)	1m 42s
latest_jdk (windows-latest, core)	4m 12s
latest_jdk (windows-latest, consumer)	8m 45s
latest_jdk (windows-latest, provider)	10m 11s
latest_jdk (windows-latest, pact-specification-test)	3m 41s
latest_jdk (macos-latest, core)	4m 46s
latest_jdk (macos-latest, consumer)	7m 14s
latest_jdk (macos-latest, provider)	8m 54s
latest_jdk (macos-latest, pact-specification-test)	2m 51s
	1h 52m 10s

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