Add ability to declare licenses in soong.

See: http://go/android-license-checking-in-soong-v2-design

Bug: 151953481
Bug: 151177513
Bug: 67772237

Change-Id: I97943de53b071cd9918679c17015ed3397c172e9

android/package_test.go

@@ -17,9 +17,11 @@ var packageTests = []struct {
 				package {
 					name: "package",
 					visibility: ["//visibility:private"],
+					licenses: ["license"],
 				}`),
 		},
 		expectedErrors: []string{
+			`top/Blueprints:5:14: unrecognized property "licenses"`,
 			`top/Blueprints:3:10: unrecognized property "name"`,
 			`top/Blueprints:4:16: unrecognized property "visibility"`,
 		},
@@ -44,9 +46,10 @@ var packageTests = []struct {
 			"top/Blueprints": []byte(`
 				package {
 					default_visibility: ["//visibility:private"],
+					default_applicable_licenses: ["license"],
 				}
 
-        package {
+			        package {
 				}`),
 		},
 		expectedErrors: []string{