Sunset cordova-plugin-legacy-whitelist

Todo (see subtasks):

1. Close out all github PRs and JIRA issues.
2. What do we need to inform Apache Infra of?
3. Update plugin README to reflect status of plugin and point to transition blog post.
4. Update coho to remove any references to the plugin.
5. Update cordova-docs to remove plugin references / remove code generation around cordova-plugin-legacy-whitelist
6. Do one final release of the plugin.
7. Ensure we deprecate the plugin in npm.