Feature Request: Add a silent option

* **Version**: `v14.18.1`
* **Platform**: `... 20.6.0 Darwin Kernel Version 20.6.0: ...; root:xnu-7195.141.2~5/RELEASE_X86_64 x86_64`

Having the ability to add a silent option (typically `-s`/`--silent` or `-q`/`--quiet`) to suppress/reduce logging would be nice. This is especially true for a command like `c8 report` since it already has an output file that can be referenced as needed. I noticed [`istanbuljs/nyc`](https://github.com/istanbuljs/nyc#combining-reports-from-multiple-runs) already has this option if that helps with implementation.