resource/aws_kms_alias: Add target_key_arn attribute

[bflad]

Simple followup to #2551 to add target_key_arn attribute to the aws_kms_alias resource as well. We would need to augment testAccCheckAWSKmsAliasExists in the acceptance testing to pass back a kms.ListAliasEntry or similar in order to properly check the new attribute value from the existing key ID value (I don't mind implementing this though).

make testacc TEST=./aws TESTARGS='-run=TestAccAWSKmsAlias'
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./aws -v -run=TestAccAWSKmsAlias -timeout 120m
=== RUN   TestAccAWSKmsAlias_importBasic
--- PASS: TestAccAWSKmsAlias_importBasic (43.47s)
=== RUN   TestAccAWSKmsAlias_basic
--- PASS: TestAccAWSKmsAlias_basic (50.60s)
=== RUN   TestAccAWSKmsAlias_name_prefix
--- PASS: TestAccAWSKmsAlias_name_prefix (39.43s)
=== RUN   TestAccAWSKmsAlias_no_name
--- PASS: TestAccAWSKmsAlias_no_name (39.46s)
=== RUN   TestAccAWSKmsAlias_multiple
--- PASS: TestAccAWSKmsAlias_multiple (38.73s)
PASS
ok  	github.com/terraform-providers/terraform-provider-aws/aws	211.737s

[catsby]

👍

[bflad]

This has been released in terraform-provider-aws version 1.8.0. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!