Add a new Fuzz message containing all the message types we want to make
available to fuzzers. Previously, testing (for example) required fields
would require modifying the fuzzer; now, it's just a matter of adding a
message with required fields as a field of the top-level Fuzz message.
Add internal/cmd/generate-corpus to codify where the fuzz seed corpus
comes from. This will simplify adding text and json fuzzers.
Rename internal/fuzz/wire to internal/fuzz/wirefuzz to minimize package
name ambiguity. Also, the addition of the Fuzz container message
invalidates the existing corpus, so using a new name seems like a good
idea.
Change-Id: I94f8f64ba93596c8e8cecb4d42bcc5b98c17d838
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/212218
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
