resource/aws_codebuild_project: Add arn attribute and improve id attribute documentation

[bflad]

Closes #5962

Changes proposed in this pull request:

• Add arn attribute to aws_codebuild_project
• Document id attribute behavior better

Output from acceptance testing:

23 tests passed (all tests)
--- PASS: TestAccAWSCodeBuildProject_Source_Type_CodePipeline (17.08s)
--- PASS: TestAccAWSCodeBuildProject_WindowsContainer (17.28s)
--- PASS: TestAccAWSCodeBuildProject_Source_Type_CodeCommit (17.61s)
--- PASS: TestAccAWSCodeBuildProject_Source_Type_S3 (17.96s)
--- PASS: TestAccAWSCodeBuildProject_importBasic (18.01s)
--- PASS: TestAccAWSCodeBuildProject_Source_Type_Bitbucket (18.10s)
--- PASS: TestAccAWSCodeBuildProject_Source_InsecureSSL (21.74s)
--- PASS: TestAccAWSCodeBuildProject_basic (25.83s)
--- PASS: TestAccAWSCodeBuildProject_BadgeEnabled (25.84s)
--- PASS: TestAccAWSCodeBuildProject_Source_Type_GitHubEnterprise (26.01s)
--- PASS: TestAccAWSCodeBuildProject_Source_Auth (25.99s)
--- PASS: TestAccAWSCodeBuildProject_Tags (29.55s)
--- PASS: TestAccAWSCodeBuildProject_Source_GitCloneDepth (29.68s)
--- PASS: TestAccAWSCodeBuildProject_Source_ReportBuildStatus (29.83s)
--- PASS: TestAccAWSCodeBuildProject_Description (30.14s)
--- PASS: TestAccAWSCodeBuildProject_Environment_EnvironmentVariable_Type (30.12s)
--- PASS: TestAccAWSCodeBuildProject_BuildTimeout (30.58s)
--- PASS: TestAccAWSCodeBuildProject_EncryptionKey (35.23s)
--- PASS: TestAccAWSCodeBuildProject_VpcConfig (37.10s)
--- PASS: TestAccAWSCodeBuildProject_Artifacts_EncryptionDisabled (24.02s)
--- PASS: TestAccAWSCodeBuildProject_SecondaryArtifacts (23.97s)
--- PASS: TestAccAWSCodeBuildProject_SecondarySources_CodeCommit (23.68s)
--- PASS: TestAccAWSCodeBuildProject_Cache (43.49s)

[bflad]

This has been released in version 1.38.0 of the AWS provider. 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!