🔧 Repository: Improve and Generalize Plugin Migration Script

### 📜 Description

We currently have a [migration script](https://github.com/backstage/community-plugins/blob/main/workspaces/repo-tools/packages/cli/src/commands/plugin/migrate.ts) under repo-tools that is designed for migrating plugins from [backstage/backstage](https://github.com/backstage/backstage). However, it is not yet generalized or fully ready for public use. The goal is to enhance and generalize this script, making it an automated option that can be leveraged by the community for migrating plugins in the future.

Some Initial Steps (might be more):
- [ ] Update references to the backstage/backstage monorepo ([example](https://github.com/backstage/community-plugins/blob/main/workspaces/repo-tools/packages/cli/src/commands/plugin/migrate.ts#L467)) to to use the path provided via the [`monorepo-path` option ](https://github.com/backstage/community-plugins/blob/main/workspaces/repo-tools/packages/cli/src/commands/index.ts#L53)
- [ ] Add [a cli option](https://github.com/backstage/community-plugins/blob/main/workspaces/repo-tools/packages/cli/src/commands/index.ts#L51) to specify the current npm scope under which the plugins are being currently published and replace that with the hardcoded `@backstage` scope in the script ([example](https://github.com/backstage/community-plugins/blob/main/workspaces/repo-tools/packages/cli/src/commands/plugin/migrate.ts#L89))
- [ ] Evaluate if the dependency changes and patches being added/changed as a part of this script are needed (Or if they need to be modified)
- [ ] Include instructions on how to use this script in [CONTRIBUTING.md](https://github.com/backstage/community-plugins/blob/main/CONTRIBUTING.md) under the [migrating a plugin](https://github.com/backstage/community-plugins/blob/main/CONTRIBUTING.md#migrating-a-plugin) section.

We might also want to look into adding checks that we look for when a new plugin is added to the repo such as if the plugins being added are on the latest backstage version etc.