This bug affected RM_StringToLongDouble and HINCRBYFLOAT.
I added tests for both cases.

Main changes:
1. Fixed string2ld to fail if string contains \0 in the middle
2. Use string2ld in getLongDoubleFromObject - No point of
   having duplicated code here

The two changes above broke RM_SaveLongDouble/RM_LoadLongDouble
because the long double string was saved with length+1 (An innocent
mistake, but it's actually a bug - The length passed to
RM_SaveLongDouble should not include the last \0).

If a blocked module client times-out (or disconnects, unblocked
by CLIENT command, etc.) we need to call moduleUnblockClient
in order to free memory allocated by the module sub-system
and blocked-client private data

Other changes:
Made blockedonkeys.tcl tests a bit more aggressive in order
to smoke-out potential memory leaks

So error message `ERR only (P)SUBSCRIBE / (P)UNSUBSCRIBE / PING / QUIT allowed in this context` will become
`ERR 'get' command submitted, but only (P)SUBSCRIBE / (P)UNSUBSCRIBE / PING / QUIT allowed in this context`

Related to #6054.

Related to #6110.

The directive tls-prefer-server-cipher is actually tls-prefer-server-ciphers in config.c. This results in a failed directive call shown below. This pull request adds the "s" in ciphers so that the directive is able to be properly called in config.c

ubuntu@ip-172-31-16-31:~/redis$ src/redis-server ./redis.conf 

*** FATAL CONFIG FILE ERROR ***
Reading the configuration file, at line 200
>>> 'tls-prefer-server-cipher yes'
Bad directive or wrong number of arguments

We exit later, so no bug fixed, but it is more correct.

See #6054, thanks to @ShooterIT for finding the issue.

This commit solves the following bug:
127.0.0.1:6379> XGROUP CREATE x grp $ MKSTREAM
OK
127.0.0.1:6379> XADD x 666 f v
"666-0"
127.0.0.1:6379> XREADGROUP GROUP grp Alice BLOCK 0 STREAMS x >
1) 1) "x"
   2) 1) 1) "666-0"
         2) 1) "f"
            2) "v"
127.0.0.1:6379> XADD x 667 f v
"667-0"
127.0.0.1:6379> XDEL x 667
(integer) 1
127.0.0.1:6379> XREADGROUP GROUP grp Alice BLOCK 0 STREAMS x >
1) 1) "x"
   2) (empty array)

The root cause is that we use s->last_id in streamCompareID
while we should use the last *valid* ID

Funcion adjustOpenFilesLimit() has an implicit parameter, which is server.maxclients.
This function aims to ajust maximum file descriptor number according to server.maxclients
by best effort, which is "bestlimit" could be lower than "maxfiles" but greater than "oldlimit".
When we try to increase "maxclients" using CONFIG SET command, we could increase maximum
file descriptor number to a bigger value without calling aeResizeSetSize the same time.
When later more and more clients connect to server, the allocated fd could be bigger and bigger,
and eventually exceeds events size of aeEventLoop.events. When new nodes joins the cluster,
new link is created, together with new fd, but when calling aeCreateFileEvent, we did not
check the return value. In this case, we have a non-null "link" but the associated fd is not
registered.

So when we dynamically set "maxclients" we could reach an inconsistency between maximum file
descriptor number of the process and server.maxclients. And later could cause cluster link and link
fd inconsistency.

While setting "maxclients" dynamically, we consider it as failed when resulting "maxclients" is not
the same as expected. We try to restore back the maximum file descriptor number when we failed to set
"maxclients" to the specified value, so that server.maxclients could act as a guard as before.

Instead of 512, use the defined max from networking.c

Fixes #6744.