* fix(command): read past error elements in IntSliceCmd
TS.MADD and CMS.INCRBY reply with an error element for a rejected item
and keep answering for the items after it. Returning on that element
left the tail of the array unread, and in a pipeline the next command
read it as its own reply.
* docs(command): note per-item errors on TSMAdd/CMSIncrBy
Also move the error-element tests next to the nil-element cases.
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Co-authored-by: Nedyalko Dyakov <1547186+ndyakov@users.noreply.github.com>