Create (API) bp2build converters for droidstubs

- The converter runs for api_bp2build, not bp2build workspace
- Since droidstubs is an internal module created by java_sdk_library,
  the conversion encompasses the latter as well
- Since droidstubs do not have an api_surface attribute, this conversion
  uses naming convention to infer the api_surface represented by the api
  file e.g. *stubs.source -> publicapi, *stubs.source.system -> systemapi)
- Also adds an SdkIntraCore enum to represent the API surface provided
  by one core module to another

There is also ongoing work to check in java_api_contribution modules in
Soong. Once we have that, we can update this converter to operate on
that module type instead

Test: go test ./bp2build
Change-Id: Ia85828e04c738d9ffcc524856d7c3034ee29bbf9

java/droidstubs_test.go

@@ -304,3 +304,45 @@ func TestDroidstubsWithSdkExtensions(t *testing.T) {
 	android.AssertStringDoesContain(t, "sdk-extensions-root present", cmdline, "--sdk-extensions-root sdk/extensions")
 	android.AssertStringDoesContain(t, "sdk-extensions-info present", cmdline, "--sdk-extensions-info sdk/extensions/info.txt")
 }
+
+func TestApiSurfaceFromDroidStubsName(t *testing.T) {
+	testCases := []struct {
+		desc               string
+		name               string
+		expectedApiSurface string
+	}{
+		{
+			desc:               "Default is publicapi",
+			name:               "mydroidstubs",
+			expectedApiSurface: "publicapi",
+		},
+		{
+			desc:               "name contains system substring",
+			name:               "mydroidstubs.system.suffix",
+			expectedApiSurface: "systemapi",
+		},
+		{
+			desc:               "name contains system_server substring",
+			name:               "mydroidstubs.system_server.suffix",
+			expectedApiSurface: "system-serverapi",
+		},
+		{
+			desc:               "name contains module_lib substring",
+			name:               "mydroidstubs.module_lib.suffix",
+			expectedApiSurface: "module-libapi",
+		},
+		{
+			desc:               "name contains test substring",
+			name:               "mydroidstubs.test.suffix",
+			expectedApiSurface: "testapi",
+		},
+		{
+			desc:               "name contains intra.core substring",
+			name:               "mydroidstubs.intra.core.suffix",
+			expectedApiSurface: "intracoreapi",
+		},
+	}
+	for _, tc := range testCases {
+		android.AssertStringEquals(t, tc.desc, tc.expectedApiSurface, bazelApiSurfaceName(tc.name))
+	}
+}