Make golden proof test data available to other languages

[mhutchinson]

https://github.com/transparency-dev/merkle/blob/main/proof/proof_test.go

The table-driven test data for TestInclusion and TestConsistency could be written out to golden files, e.g. as json. These could then be available for tests of inclusion and consistency in other languages.

This would enable sigstore/sigstore-rs#285 to have a clear exit criteria for correctness. I imagine other languages would also benefit from this.

[mhutchinson]

The original comment should really have pointed at https://github.com/transparency-dev/merkle/blob/main/proof/verify_test.go which contains the tests for verifying the proofs, instead of constructing them.