Module API for PUBLISH, FLUSHALL, RANDOMKEY, DBSIZE

Modules: Test RedisModule_BlockClientOnKeys

Modules hooks: complete missing hooks for the initial set of hooks

See #6525, this likely creates a NULL deference if the client was
terminated by Redis between the creation of the blocked client and the
creation of the thread safe context.

Using the is_key_ready() callback plus the reply callback later, creates
different issues AFAIK:

1. More complex API.
2. We need to call the reply callback() ASAP if the is_key_ready()
interface returned success, however the internals do not work in that
way, so when the reply callback is called the setup could be different.
To fix that, there is to break the current design that handles the
unblocked clients asyncrhonously, and run the list ASAP.

Now we handle propagation when we free the context.

* replication hooks: role change, master link status, replica online/offline
* persistence hooks: saving, loading, loading progress
* misc hooks: cron loop, shutdown, module loaded/unloaded
* change the way hooks test work, and add tests for all of the above

startLoading() now gets flag indicating what is loaded.
stopLoading() now gets an indication of success or failure.
adding startSaving() and stopSaving() with similar args and role.

Module API for explicit SignalModifiedKey instead of implicit one.

Add Github action for CI

Fix compilation error introduced by cee6dead

Module api RM_CallArgv and test

Need to add calls to REDISMODULE_API_FUNC...

Modules: Allow notifying custom keyspace events

Adding a test for coverage for RM_Call in a new "misc" unit
to be used for various short simple tests

also solves compilation warnings in redismodule.h and fork.c

Also, add an API for getting server.notify_keyspace_events

Other (unrelated) changes:
Add RM_GetKeynameFromModuleKey

This commit also fixes an uninitialized module struct member (that luckily never got released)

Make module tests pass with valgrind, and fix a leak in diskless load

Modules: improve tests Makefile.

Module API for LatencyAddSample

Fix some minor typos in comments

fix comment typo in redis-cli.c

Typo fix: kill -> still

Introduce ReplyWithVerbatimString, ReplyWithEmptyArray, ReplyWithNull…

Modules: make unloading module more safe

Introduce ReplyWithVerbatimString, ReplyWithEmptyArray, ReplyWithNullArray and ReplyWithEmptyString to redis module API