* add ad for compute-vm refactor
* Exclue nic_type from validated fields, add split of main.tf and template.tf
* boot disk
* fix examples and fixtures
* attached disks
* fix further examples and module-level tests
* remove extra file
* fix mig examples
* finish refactoring variables
* align fast and other modules
* refactor(compute-vm): align examples and ADR with the newly implemented interface
This commit addresses the remaining references of the `instance_type` and `confidential_compute` parameters in the testing environment and updates the ADR.
* feat(compute-vm): add network_performance_config to instance and templates
This change implements the usage of the `network_performance_tier` variable we added earlier into the actual Terraform resources.
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Co-authored-by: Wiktor Niesiobędzki <wiktorn@google.com>
