* refactor(net-lb-app-ext): improve configurability and resource references
- Allow overriding names for backend buckets and instance groups
- Add optional per-group description with default value
- Use self_link for instance group backend references
- Fix HTTP proxy name to use http_proxy_config
* reverted the instance group reference in backend service back to id instead of self link
* updated all the lb modules for unmanaged instance groups to have flexible names and proper refactorization of http_proxy_cofig in each module
* removed the description variable
* updated the readme.md for the net-lb-app-ext-regional module
* fixed the linting error for the change in versions.tf
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Co-authored-by: Julio Castillo <jccb@google.com>
Co-authored-by: Ludovico Magnocavallo <ludomagno@google.com>
