Terraform 7456 spanner database deletion protection

[modular-magician]

Fixes #7456.

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• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

spanner: added `deletion_protection` field to `google_spanner_database` to make deleting them require an explicit intent.

spanner: `google_spanner_database` resources now cannot be destroyed unless `deletion_protection = false` is set in state for the resource.

Derived from GoogleCloudPlatform/magic-modules#4117

[ghost]

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