Add fuzz test

[edznux-dd]

What does this PR do?

This PR adds a fuzz test (and a regression test with its first crash.

Motivation

Helps to make sure sketches-go doesn't panic on any payload.

Additional Notes

The regression test will try to allocate a huge amount of memory, and fail / crash trying. And because it's a runtime panic, as far as I can tell, you can't recover from it.

=== RUN   TestRegression
fatal error: runtime: out of memory

You can run the fuzzer locally, go test -fuzz=FuzzDecodeDDSketch -run=FuzzDecodeDDSketch

Associated Issue