limit how much data we read from a command substitution #3822
Description
At the moment we don't impose any limits on the amount of data that we accept from read or a command substitution (e.g., (cmd)). Issue #3712 proposes setting a limit of 100 MiB for any single read execution. This issue is to discuss whether the same, or a similar, limit should be imposed on command substitution output. See issue #3817 for examples of what can happen without such a limit.