Fix protocol parsing on 'ldbReplParseCommand' (CVE-2021-32672) (#9590)

The protocol parsing on 'ldbReplParseCommand' (LUA debugging)
Assumed protocol correctness. This means that if the following
is given:
*1
$100
test
The parser will try to read additional 94 unallocated bytes after
the client buffer.
This commit fixes this issue by validating that there are actually enough
bytes to read. It also limits the amount of data that can be sent by
the debugger client to 1M so the client will not be able to explode
the memory.

Co-authored-by: meir@redislabs.com <meir@redislabs.com>