Updated swagger-core to version 1.6.1 to support 'parseValue' in 'extensions'

[ankrim]

In version 1.6.1 swagger-core (and swagger-annotations) added support for the parseValue property as part of the @ExtensionProperty annotation.
If parseValue is true the provided value is treated as json and it's parsed into the generated OpenAPI file as a nested object or an array (instead of as a string).

In this PR I upgraded the swagger-core library from 1.5.21 to 1.6.1 and updated the relevant tests (same as in https://github.com/kongchen/swagger-maven-plugin/pull/582/files).

I also upgraded other libraries to try to make mvn install work (but it doesn't) and run the tests in Intellij (that works), so these changes might not be needed if mvn install works in the CI.
I was able to make mvn install -DskipTests work with the additional libraries upgrades only if I manually disable the check-java16-sun execution (in animal-sniffer-maven-plugin).
Please let me know if you want to keep these additional upgrades or remove them.