Update `JacksonTester` so that the JsonPath instance is explicitly configured
with both a `JacksonJsonProvider` and a `JacksonMappingProvider`.

Prior to this commit, the handling of special characters was not symmetrical
between the serialization (handled via the JacksonTester) and the parsing (handled
via JsonPath) due to the fact that JsonPath used `SimpleJson` as its parser.

See gh-16629