[C++][Parquet] Fuzz encrypted files

[pitrou]

Describe the enhancement requested

Currently, if given an encrypted file (whether valid or invalid), the Parquet fuzz target will bail out almost immediately since it does not have any decryption key configured.

We should improve the fuzzing setup so that we are able to successfully decrypt valid Parquet files, and fail gracefully on invalid files, which will let the fuzzer explore the Parquet encryption code.

Component(s)

C++, Parquet

[pitrou]

Issue resolved by pull request 48336
#48336