Allow raw output from `sls invoke` without JSON encoding

Is there an existing issue for this?

• I have searched existing issues, it hasn't been reported yet

Use case description

It would be useful to be able to able to get the raw output from the invoke command, similar to how the --raw switch works for input. The invoke and the invoke local commands stringify the output.

At the moment to generate a CSV file the output must be unstringified:

sls invoke local -f export --data XXX | node -e 'console.log(JSON.parse(fs.readFileSync("/dev/stdin", "utf-8")));' > out.csv

Proposed solution (optional)

Adding a --rawOutput command switch.

Start with lib/plugins/aws/invoke.js and lib/plugins/aws/invoke-local/index.js, where the issue identifies the output stringification. Trace how the invoke commands parse options and emit output, then add the proposed --rawOutput behavior while preserving the existing default. Done means both commands can emit raw output without JSON encoding when the switch is used.