rdb 12 (redis 7.4+): add support for hash with field expiration

[bpint]

redis 7.4+ introduced HFE, i. e., hash / listpack with field expiration, with type identifier 22, 23, 24, and 25 in rdb format 12.

this add basic support for rdb 12 compatible with redis 7.4+,

a) HashObjectEx type, which can be formatted as json, as well as RESP commands (obj2cmd)
b) decoding hash / listpack HFE from rdb
c) encoding HashObjectEx as rdb (hash HFE)

[HDT3213]

1. Could you add some test cases?
2. I tend not to add HashObjectEx; instead, I prefer to add the FieldExpirations map[string]int64 field to the existing HashObject to maintain compatibility.

[bpint]

i resubmitted the pr. now,

a) HashObject with field expirations instead of HashObjectEx, as your wish
b) rdb samples as test cases of hash and listpack with hfe are added
c) i found a bug in my obj2cmd and fixed it

[HDT3213]

Looks good to me! Thanks for your contribution!