make database_encryption updateable

[megan07]

Fixes hashicorp/terraform-provider-google#6733

Release Note Template for Downstream PRs (will be copied)

container: added the ability to update `database_encryption` without recreating the cluster.

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 1 file changed, 25 insertions(+), 3 deletions(-))
Terraform Beta: Diff ( 1 file changed, 25 insertions(+), 3 deletions(-))

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=131328"

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 2 files changed, 35 insertions(+), 5 deletions(-))
Terraform Beta: Diff ( 2 files changed, 35 insertions(+), 5 deletions(-))

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=131342"

[modular-magician]

I have triggered VCR tests in RECORDING mode for the following tests that failed during VCR: TestAccContainerCluster_withDatabaseEncryption|TestAccEndpointsService_basic You can view the result here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=131344"