Replacing std::hash to ensure portability of interpolation files

[Jean1995]

PROPOSAL uses std::hash to calculate hashes. However, the implementation of std::hash is different for clang and gcc (and therefore the resulting hashes are different). This causes the names of the interpolation table files to differ on different operating systems, e.g. they are not really portable.

From the documentation of std::hash:

The actual hash functions are implementation-dependent [...]
Hash functions are only required to produce the same result for the same input within a single execution of a program [...]

It should be more than enough to use something like sha512, I found stbrumme/hash-library as one set of implementations of hashing algorithms.

Hashing std::string (for names) is of course straight forward, but I probably need to think more about a good way to hash integers and especially floating-points numbers (e.g. for the particle masses).

[maxnoe]

https://abseil.io/docs/cpp/guides/hash

[MaxSac]

Not the solution but maybe nice to know 😅
https://www.boost.org/doc/libs/master/libs/uuid/doc/uuid.html

[HDembinski]

I am slightly biased, but would of course propose boost::container_hash https://github.com/boostorg/container_hash

Hash values are not promised to be stable forever, but are historically fairly stable and the library includes a test that the result of the implementation is the same everywhere. Sounds like boost is the right solution as usual.
https://www.boost.org/doc/libs/1_83_0/libs/container_hash/doc/html/hash.html#notes_hash_value_stability