repl: fix crash with large buffer tab completion
If the buffer or array is too large to completion, make a dummy smallest substitute object for it and emit a warning.
Fixes: https://github.com/nodejs/node/issues/3136
Checklist
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make -j4 test
(UNIX) -
tests and/or benchmarks are included -
commit message follows commit guidelines
Affected core subsystem(s)
repl