feat(`forge test`) add an optional `--json-file` argument to write both to `stdout` and to a JSON file

[adhusson]

Component

Forge

Describe the feature you would like

When running tests in a CI, it is useful to both show the human-readable output on stdout and write a JSON file to be processed at later stages by the CI.

Right now, the only way to output both is either 1) to run forge test twice, or 2) to run forge test --json | myProcessingTool, where myProcessingTool writes a JSON file and format the JSON back to human-readable output.

With forge test --json-file path/to/file you would get both outputs.