Overhaul CLI functionality with urfave/cli (chainguard-dev#436)

* Overhaul CLI functionality with urfave/cli

Signed-off-by: egibs <[email protected]>

* Use flags to separate image/path scanning

Signed-off-by: egibs <[email protected]>

* Small tweaks

Signed-off-by: egibs <[email protected]>

* Update test data refresh script, handle scan edge cases

Signed-off-by: egibs <[email protected]>

* Simplify risk level map

Signed-off-by: egibs <[email protected]>

* Update wording/formatting

Signed-off-by: egibs <[email protected]>

* Clean up arg parsing

Signed-off-by: egibs <[email protected]>

* Clean up version string

Signed-off-by: egibs <[email protected]>

* Add separate analyze command for displaying all rule matches

Signed-off-by: egibs <[email protected]>

* Appease the linter

Signed-off-by: egibs <[email protected]>

* Scan flag is not needed

Signed-off-by: egibs <[email protected]>

* Filter out < 3 risk scores when running a scan

Signed-off-by: egibs <[email protected]>

* Severity -> risk

Signed-off-by: egibs <[email protected]>

* Only require flags for analyzing/scanning images

Signed-off-by: egibs <[email protected]>

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Signed-off-by: egibs <[email protected]>
Signed-off-by: Evan Gibler <[email protected]>