Implement hide-secrets flag for run command

[remorses]

Implements #326

[remorses]

I can add tests for ReplaceTransformer if you want, i copied that code from here

[Piccirello]

I'm having difficulty understanding the practical use case for this, beyond demos. Why would a user want invalid values to be injected? I think a more pragmatic solution would be to support specifying an allowlist of secrets that should be injected (#322).

[remorses]

This pr does not inject invalid values, it simply hides them from the terminal output, the env variables remain the same

some use cases

• Making sure CI logs do not contain secrets (anyone that can see your logs could steal your secrets, very dangerous)
• streaming on twitch or demos

[benhylak]

this is nice.