feat: Add R cataloger (#1790)

Add a cataloger that detects installed R packages by looking for DESCRIPTION
files. The base R package is now picked up in coverageImage tests in
test/cli/packages_cmd_test.go, so increment expected package counts for the
tests that use that image.

Signed-off-by: Will Murphy <will.murphy@anchore.com>

syft/pkg/cataloger/r/package.go

@@ -0,0 +1,32 @@
+package r
+
+import (
+	"github.com/anchore/packageurl-go"
+	"github.com/anchore/syft/syft/pkg"
+	"github.com/anchore/syft/syft/source"
+)
+
+func newPackage(pd parseData, locations ...source.Location) pkg.Package {
+	locationSet := source.NewLocationSet()
+	for _, loc := range locations {
+		locationSet.Add(loc.WithAnnotation(pkg.EvidenceAnnotationKey, pkg.PrimaryEvidenceAnnotation))
+	}
+	result := pkg.Package{
+		Name:         pd.Package,
+		Version:      pd.Version,
+		Locations:    locationSet,
+		Licenses:     []string{pd.License},
+		Language:     pkg.R,
+		Type:         pkg.Rpkg,
+		PURL:         packageURL(pd),
+		MetadataType: pkg.RDescriptionFileMetadataType,
+		Metadata:     pd.RDescriptionFileMetadata,
+	}
+
+	result.SetID()
+	return result
+}
+
+func packageURL(m parseData) string {
+	return packageurl.NewPackageURL("cran", "", m.Package, m.Version, nil, "").ToString()
+}