Fix: unmarshal key values in Java, Go, and Conan metadata (#2603)

Previously, Syft represented several metadata fields as map[string]string,
however this representation erased ordering, so Syft now represents these values
as []KeyValue. Add custom unmarshaling so that JSON that was written by
older versions of Syft using the map[string]string representation can be parsed
into the new []KeyValue representation.

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

syft/pkg/java_test.go

@@ -3,6 +3,7 @@ package pkg
 import (
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -109,3 +110,103 @@ func TestPomProperties_PkgTypeIndicated(t *testing.T) {
 		})
 	}
 }
+
+func Test_legacyJavaManifest_toNewManifest(t *testing.T) {
+	tests := []struct {
+		name string
+		lm   legacyJavaManifest
+		want JavaManifest
+	}{
+		{
+			name: "empty",
+			lm:   legacyJavaManifest{},
+			want: JavaManifest{},
+		},
+		{
+			name: "main sections are sorted",
+			lm: legacyJavaManifest{
+				Main: map[string]string{
+					"a key": "a value",
+					"b key": "b value",
+					"c key": "c value",
+				},
+			},
+			want: JavaManifest{Main: KeyValues{
+				{
+					Key:   "a key",
+					Value: "a value",
+				},
+				{
+					Key:   "b key",
+					Value: "b value",
+				},
+				{
+					Key:   "c key",
+					Value: "c value",
+				},
+			}},
+		},
+		{
+			name: "named sections have their name in the result",
+			lm: legacyJavaManifest{
+				NamedSections: map[string]map[string]string{
+					"a section": {
+						"a key": "a value",
+						"b key": "b value",
+						"c key": "c value",
+					},
+					"b section": {
+						"d key": "d value",
+						"e key": "e value",
+						"f key": "f value",
+					},
+				},
+			},
+			want: JavaManifest{Sections: []KeyValues{
+				{
+					{
+						Key:   "Name",
+						Value: "a section",
+					},
+					{
+						Key:   "a key",
+						Value: "a value",
+					},
+					{
+						Key:   "b key",
+						Value: "b value",
+					},
+					{
+						Key:   "c key",
+						Value: "c value",
+					},
+				},
+				{
+					{
+						Key:   "Name",
+						Value: "b section",
+					},
+					{
+						Key:   "d key",
+						Value: "d value",
+					},
+					{
+						Key:   "e key",
+						Value: "e value",
+					},
+					{
+						Key:   "f key",
+						Value: "f value",
+					},
+				},
+			}},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if diff := cmp.Diff(tt.want, tt.lm.toNewManifest()); diff != "" {
+				t.Errorf("unexpected diff in manifest (-want +got):\n%s", diff)
+			}
+		})
+	}
+}