Internalize majority of cmd package (#2533)

* internalize majority of cmd package and migrate integration tests

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* add internal api encoder

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* create internal representation of all formats

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* export capability to get default encoders

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

* restore test fixtures

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

---------

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

cmd/syft/internal/test/integration/distro_test.go

@@ -0,0 +1,25 @@
+package integration
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/anchore/syft/syft/linux"
+	"github.com/anchore/syft/syft/source"
+)
+
+func TestDistroImage(t *testing.T) {
+	sbom, _ := catalogFixtureImage(t, "image-distro-id", source.SquashedScope)
+
+	expected := &linux.Release{
+		PrettyName: "BusyBox v1.31.1",
+		Name:       "busybox",
+		ID:         "busybox",
+		IDLike:     []string{"busybox"},
+		Version:    "1.31.1",
+		VersionID:  "1.31.1",
+	}
+
+	assert.Equal(t, expected, sbom.Artifacts.LinuxDistribution)
+}