odin: rename backup notifications key arn and make optional

[matt-mercer]

Description

• renamed the variable bootstrap_kms_key_arn to backup_notifications_kms_key_arn in source module and allowed this to be optional, so the module will create a kms key if one not supplied
• added trivy and tf-lint and supporting pre-commit.yaml to run

breaking in the variable rename, but non-breaking from a resource perspective

Context

the previous bootstrap_kms_key_arn variable is confusing in as to the purpose, and since this key is required by the module, it seems sensible to get the module to auto create this key, but support passing in the notifications key arn for backward compatibility

since this is a central module, we should be running trivy and tf-lint on these to ensure quality and security locally

Type of changes

• Refactoring (non-breaking change)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would change existing functionality)
• Bug fix (non-breaking change which fixes an issue)

Checklist