Switch to using native fuzz tests

[joshuagl]

#275 introduced some JSON unmarshal hardening and uses a fuzzer to generate test data for the hardening.

We should port the test to use the native fuzzer available in Go 1.18 (and newer) to reduce our third-party dependencies.

Originally posted by @Zenithar in #275 (comment)

[abs007]

Does this mean importing the native fuzzer in place of the 3rd party fuzzer in the source code and then running go mod tidy?
(New to golang. Hence a bit verbose)

[joshuagl]

I'm not familiar with the state of fuzzing in Go, but it might also be necessary to port the fuzzing logic to the API of the native fuzzer.

[rdimitrov]

Closing since the code base changed and we no longer have the same tests.

Thanks for raising this 👍