Disk encryption settings should not refer to launch template

[Nuru]

The variables launch_template_disk_encryption_enabled and launch_template_disk_encryption_kms_key_id are poorly named. The fact that these settings affect the launch template is an implementation detail and should not be reflected in the names.

Please rename them

• launch_template_disk_encryption_enabled -> disk_encryption_enabled
• launch_template_disk_encryption_kms_key_id -> disk_encryption_kms_key_id

Notes

1. Backward compatibility can be maintained by leaving the existing variables in place but changing the defaults to null, and giving them priority when they are non-null
2. Because of Terraform Module Registry incorrectly shows Inputs as required if default = null hashicorp/terraform#21417, variables with defaults of null are listed as required, so this change should probably wait until that bug is fixed, otherwise the documentation will show the strange result that these deprecated variables are required inputs