#13495 introduced a change to reply -LOADING while flushing existing db on a replica. Some of our tests are
 sensitive to this change and do no expect -LOADING reply.

Fixing a couple of tests that fail time to time.

### New Features in binary distributions

- 7 new data structures: JSON, Time series, Bloom filter, Cuckoo filter,
Count-min sketch, Top-k, t-digest
- Redis scalable query engine (including vector search)

### Potentially breaking changes

- #12272 `GETRANGE` returns an empty bulk when the negative end index is
out of range
- #12395 Optimize `SCAN` command when matching data type

### Bug fixes

- #13510 Fix `RM_RdbLoad` to enable AOF after RDB loading is completed
- #13489 `ACL CAT` - return module commands
- #13476 Fix a race condition in the `cache_memory` of `functionsLibCtx`
- #13473 Fix incorrect lag due to trimming stream via `XTRIM` command
- #13338 Fix incorrect lag field in `XINFO` when tombstone is after the
`last_id` of the consume group
- #13470 On `HDEL` of last field - update the global hash field
expiration data structure
- #13465 Cluster: Pass extensions to node if extension processing is
handled by it
- #13443 Cluster: Ensure validity of myself when loading cluster config
- #13422 Cluster: Fix `CLUSTER SHARDS` command returns empty array

### Modules API

- #13509 New API calls: `RM_DefragAllocRaw`, `RM_DefragFreeRaw`, and
`RM_RegisterDefragCallbacks` - defrag API to allocate and free raw
memory

### Performance and resource utilization improvements

- #13503 Avoid overhead of comparison function pointer calls in listpack
`lpFind`
- #13505 Optimize `STRING` datatype write commands
- #13499 Optimize `SMEMBERS` command
- #13494 Optimize `GEO*` commands reply
- #13490 Optimize `HELLO` command
- #13488 Optimize client query buffer
- #12395 Optimize `SCAN` command when matching data type
- #13529 Optimize `LREM`, `LPOS`, `LINSERT`, and `LINDEX` commands
- #13516 Optimize `LRANGE` and other commands that perform several
writes to client buffers per call
- #13431 Avoid `used_memory` contention when updating from multiple
threads

### Other general improvements

- #13495 Reply `-LOADING` on replica while flushing the db

### CLI tools

- #13411 redis-cli: Fix wrong `dbnum` showed after the client
reconnected

### Notes

- No backward compatibility for replication or persistence.
- Additional distributions, upgrade paths, features, and improvements
will be introduced in upcoming pre-releases.
- With the GA release of 8.0 we will deprecate Redis Stack.

In #13495, we introduced a feature to
reply -LOADING while flushing a large db on a replica.
While `_dictClear()` is in progress, it calls a callback for every 65k
items and we yield back to eventloop to reply -LOADING.

This change has made some tests unstable as those tests don't expect new
-LOADING reply.
One observation, inside `_dictClear()`, we call the callback even if db
has a few keys. Most tests run with small amount of keys. So, each
replication and cluster test has to handle potential -LOADING reply now.

This PR changes this behavior, skips calling callback when `i=0` to
stabilize replication tests.
Callback will be called after the first 65k items. Most tests use less
than 65k keys and they won't get -LOADING reply.

In #13495, we introduced a feature to
reply -LOADING while flushing a large db on a replica.
While `_dictClear()` is in progress, it calls a callback for every 65k
items and we yield back to eventloop to reply -LOADING.

This change has made some tests unstable as those tests don't expect new
-LOADING reply.
One observation, inside `_dictClear()`, we call the callback even if db
has a few keys. Most tests run with small amount of keys. So, each
replication and cluster test has to handle potential -LOADING reply now.

This PR changes this behavior, skips calling callback when `i=0` to
stabilize replication tests.
Callback will be called after the first 65k items. Most tests use less
than 65k keys and they won't get -LOADING reply.

When the diskless load configuration is set to on-empty-db, we retain a
pointer to the function library context. When emptyData() is called, it
frees this function library context pointer, leading to a use-after-free
situation.

I refactored code to ensure that emptyData() is called first, followed
by retrieving the valid pointer to the function library context.

Refactored code should not introduce any runtime implications.

Bug introduced by #13495 (Redis 8.0)

Co-authored-by: Oran Agra <[email protected]>