Fix soong for go test ./...

Fix various issues that prevent building or running tests with the
Go tools:

Remove testing/test_spec_proto/go.mod.  There's already a go.mod at
the top level, and adding testing/test_spec_proto/go.mod breaks
compiling with the Go tools in IntelliJ or from the command line.

Fix go vet issues when trying to print []DataPath.

Fix aconfig_conversion_test.go and add it to Android.bp so it runs
in presubmit.

Test: go test ./...
Change-Id: I18af2f05631446fe507744a2951e4b02c7ab59be

bp2build/Android.bp

@@ -6,6 +6,7 @@ bootstrap_go_package {
     name: "soong-bp2build",
     pkgPath: "android/soong/bp2build",
     srcs: [
+        "aconfig_conversion_test.go",
         "androidbp_to_build_templates.go",
         "bp2build.go",
         "bp2build_product_config.go",
@@ -21,6 +22,7 @@ bootstrap_go_package {
     deps: [
         "blueprint-bootstrap",
         "soong-aidl-library",
+        "soong-aconfig",
         "soong-android",
         "soong-android-allowlists",
         "soong-android-soongconfig",

bp2build/aconfig_conversion_test.go

@@ -156,7 +156,7 @@ func TestJavaAconfigLibrary(t *testing.T) {
 			name: "foo",
 			aconfig_declarations: "foo_aconfig_declarations",
 			libs: ["foo_java_library"],
-			test: true,
+			mode: "test",
 	}
 	`
 	expectedBazelTargets := []string{
@@ -184,7 +184,6 @@ func TestJavaAconfigLibrary(t *testing.T) {
 			AttrNameToString{
 				"aconfig_declarations":   `":foo_aconfig_declarations"`,
 				"libs":                   `[":foo_java_library-neverlink"]`,
-				"test":                   `True`,
 				"sdk_version":            `"system_current"`,
 				"target_compatible_with": `["//build/bazel_common_rules/platforms/os:android"]`,
 			},
@@ -213,7 +212,7 @@ func TestJavaAconfigLibraryAsTaggedOutput(t *testing.T) {
 	java_aconfig_library {
 			name: "foo_aconfig_library",
 			aconfig_declarations: "foo_aconfig_declarations",
-			test: true,
+			mode: "test",
 	}
 	`
 	expectedBazelTargets := []string{
@@ -230,7 +229,6 @@ func TestJavaAconfigLibraryAsTaggedOutput(t *testing.T) {
 			"foo_aconfig_library",
 			AttrNameToString{
 				"aconfig_declarations":   `":foo_aconfig_declarations"`,
-				"test":                   `True`,
 				"sdk_version":            `"system_current"`,
 				"target_compatible_with": `["//build/bazel_common_rules/platforms/os:android"]`,
 			},