add --stdout flag for simultaneous file and console output

[u-ways]

Background

This PR adds a new --stdout flag that allows users to specify an output format for stdout while also writing a different format to a file using the --file flag.

Tip

This enables workflows where users want both a human-readable table output in the console and a machine-readable format (like SARIF or JSON) saved to a file.

Usage

# Write SARIF to a file while displaying table format in the terminal
grype <image> -o sarif --file grype-scan-results.sarif --stdout table

# Write JSON to a file while displaying table format in the terminal
grype <image> -o json --file results.json --stdout table

# Write CycloneDX to a file while displaying table format in the terminal
grype <image> -o cyclonedx-json --file sbom.json --stdout table

Why?

Because I ended up having to run Grype twice to get the nice table output:

$GRYPE_CMD sbom:$GRYPE_SBOM_PATH $GRYPE_CLI_OVERRIDE_ARGS -o table > $SUMMARY_FILE
$GRYPE_CMD sbom:$GRYPE_SBOM_PATH $GRYPE_CLI_OVERRIDE_ARGS -o sarif --file grype-scan-results.sarif

Which I prefer to have for concise GH summaries.