Fix test hypothesis

[cunla]

TestServer:

• FLUSHDB ASYNC not supported (Assuming SYNC also not supported)
• FLUSHALL ASYNC not supported (Assuming SYNC also not supported)
  ==> Removing ASYNC parameter

TestHash:

• HEXPIRE do not support nx/xx/gt/lt.
• HPEXPIRE not supported.
  ==> Removed from test.

Remaining:

• TestString
  • dragonfly raised: string exceeds maximum allowed size, fakeredis support strings up to 512 * 1024 * 1024.
• TestList
  • dragonfly raised: One or more scores can't be converted into double

[romange]

Thank @cunla . Let's:

1. TestServer - agree these are not important for Dragonfly (its flush operation is always asynchronous but the api call is waiting till the operation ends).
2. HEXPIRE - agree, we do not strive for Redis 8 compatibility at this point.
3. TestString =- yeah, we are more restrictive. have not heard much complains about it. See https://github.com/dragonflydb/dragonfly/blob/main/docs/differences.md#string-lengths-indices for more details.
4. TestList - if I remember correctly, it happens during SORT and it's consistent with Redis/Valkey. I am looking at it again now.

[romange]

@cunla I am confirming again that the sequence:

lpush foo '\00'
sort foo

fails in sort for both Dragonfly and Redis. Seems that the problem in test?

[romange]

@cunla I fixed the crash. Please rebase 🙏🏼