OSV-2020-670 Memcpy-param-overlap in ot::Cli::CoapSecure::Process

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=12679 Crash type: Memcpy-param-overlap Crash state: ot::Cli::CoapSecure::Process ot::Cli::Interpreter::ProcessCoapSecure ot::Cli::Interpreter::ProcessLine...