Mirrors the C++ enum CompressionLevel in pke/constants-defs.h.
Note that the values start at 2, not 0: the header explains that
compression levels 0 and 1 are not supported and that the remaining
values are deliberately not renumbered.
Value
A named list of 2 integer scalars, each the value of the
OpenFHE C++ enumerator of the same name, naming how far a
ciphertext is compressed before the interactive bootstrapping
round-trip: COMPACT (2) sends the least data but is only safe
when the result is decrypted immediately, while SLACK (3) leaves
room for further computation on the result. Pass an element as the
interactive_boot_compression_level argument of CKKSParams() or
fhe_context().