Add gradle_module to plugin list expected output files

Add the gradle_module handler entry to the expected --list-packages
output files so that test_package_list_command passes. Also add
plugins_list.txt for macOS (non-Linux) test runs.

Signed-off-by: Devang Pratap Singh <devangpratapsingh@outlook.com>
Signed-off-by: devangpratap <115096812+devangpratap@users.noreply.github.com>

Author: devangpratap

tests/packagedcode/data/plugin/plugins_list_linux.txt

@@ -552,6 +552,13 @@ Package type:  maven
   description:       Gradle build script
   path_patterns:    '*/build.gradle', '*/build.gradle.kts'
 --------------------------------------------
+Package type:  maven
+  datasource_id:     gradle_module
+  documentation URL: https://github.com/gradle/gradle/blob/master/subprojects/docs/src/docs/design/gradle-module-metadata-latest-specification.md
+  primary language:  Java
+  description:       Gradle module metadata
+  path_patterns:    '*.module'
+--------------------------------------------
 Package type:  maven
   datasource_id:     maven_pom
   documentation URL: https://maven.apache.org/pom.html