[java-cloud-bom] Create script to update javaModulesMetadata.yaml regularly

https://github.com/googleapis/java-cloud-bom/blob/main/libraries-bom-table-generation/javaModulesMetadata.yaml was created with a one-time scrape of each module's `.repo-metadata.json` file. It would be better to create a script as part of the https://github.com/googleapis/java-cloud-bom/blob/main/.github/workflows/update-readme-table.yaml job that updates this file so that it is automatically updated whenever a `.repo-metadata.json` file is updated or created.