This commit switches UID hashing from md5 to a highway hash. It also
moves the salt value out of the file plugin - and makes it
installation-specific instead - it is moved to the global namespace.
There now are digest hash functions to make "static"
installation-specific hashes that are stable over workers available to
everyone; hashes can be 64, 128 or 256 bits in size.
Due to the fact that we switch the file hashing algorithm, all file
hashes change.
The underlyigng algorithm that is used for hashing is highwayhash-128,
which is significantly faster than md5.
intermediate chains that it encounters on the wire and use those to try
to validate chains that might be missing intermediate certificates.
This vastly improves the number of certificates that Bro can validate.
The only drawback is that now validation behavior is not entirely
predictable anymore - the certificate of a server can fail to validate
when Bro just started up (due to the intermediate missing), and succeed
later, when the intermediate can be found in the cache.
Has been tested on big-ish clusters and should not introduce any
performance problems.
