Add eventbus to cloudwatch event target

[gdavison]

Completes work from #12887 to add custom event bus support to CloudWatch Events targets.

Includes part of #15727

Relates #12887
Relates #9330

Release note for CHANGELOG:

* resource/aws_cloudwatch_event_target: Add `event_bus_name`

Output from acceptance testing:

$ make testacc TESTARGS='-run=TestAccAWSCloudWatchEventTarget_'

--- PASS: TestAccAWSCloudWatchEventTarget_disappears (138.10s)
--- PASS: TestAccAWSCloudWatchEventTarget_sqs (165.99s)
--- PASS: TestAccAWSCloudWatchEventTarget_GeneratedTargetId (171.23s)
--- PASS: TestAccAWSCloudWatchEventTarget_ssmDocument (173.08s)
--- PASS: TestAccAWSCloudWatchEventTarget_input_transformer (196.57s)
--- PASS: TestAccAWSCloudWatchEventTarget_kinesis (203.97s)
--- PASS: TestAccAWSCloudWatchEventTarget_full (205.36s)
--- FAIL: TestAccAWSCloudWatchEventTarget_ecs (206.58s)
--- PASS: TestAccAWSCloudWatchEventTarget_EventBusName (217.55s)
--- FAIL: TestAccAWSCloudWatchEventTarget_ecsWithBlankTaskCount (221.65s)
--- PASS: TestAccAWSCloudWatchEventTarget_basic (245.43s)
--- PASS: TestAccAWSCloudWatchEventTarget_batch (270.71s)

TestAccAWSCloudWatchEventTarget_ecs and TestAccAWSCloudWatchEventTarget_ecsWithBlankTaskCount are pre-existing failures (#15652)

[abonawit]

Hi I was just wondering if there is a timeline for this to be merged. I am working on some terraform that requires custom bus support for targets. Thank you for all of your work on this thus far!

[bflad]

Looks good 🚀

Output from acceptance testing in AWS Commercial:

--- PASS: TestAccAWSCloudWatchEventTarget_basic (49.40s)
--- PASS: TestAccAWSCloudWatchEventTarget_batch (143.71s)
--- PASS: TestAccAWSCloudWatchEventTarget_disappears (18.72s)
--- PASS: TestAccAWSCloudWatchEventTarget_ecs (38.44s)
--- PASS: TestAccAWSCloudWatchEventTarget_ecsWithBlankTaskCount (37.95s)
--- PASS: TestAccAWSCloudWatchEventTarget_EventBusName (41.19s)
--- PASS: TestAccAWSCloudWatchEventTarget_full (63.69s)
--- PASS: TestAccAWSCloudWatchEventTarget_GeneratedTargetId (22.62s)
--- PASS: TestAccAWSCloudWatchEventTarget_input_transformer (46.70s)
--- PASS: TestAccAWSCloudWatchEventTarget_inputTransformerJsonString (52.47s)
--- PASS: TestAccAWSCloudWatchEventTarget_kinesis (63.79s)
--- PASS: TestAccAWSCloudWatchEventTarget_sqs (21.42s)
--- PASS: TestAccAWSCloudWatchEventTarget_ssmDocument (24.79s)

Output from acceptance testing in AWS GovCloud (US):

--- PASS: TestAccAWSCloudWatchEventTarget_basic (52.62s)
--- PASS: TestAccAWSCloudWatchEventTarget_batch (89.64s)
--- PASS: TestAccAWSCloudWatchEventTarget_disappears (19.71s)
--- PASS: TestAccAWSCloudWatchEventTarget_ecs (39.90s)
--- PASS: TestAccAWSCloudWatchEventTarget_ecsWithBlankTaskCount (39.95s)
--- PASS: TestAccAWSCloudWatchEventTarget_EventBusName (44.55s)
--- PASS: TestAccAWSCloudWatchEventTarget_full (66.55s)
--- PASS: TestAccAWSCloudWatchEventTarget_GeneratedTargetId (22.58s)
--- PASS: TestAccAWSCloudWatchEventTarget_input_transformer (48.28s)
--- PASS: TestAccAWSCloudWatchEventTarget_inputTransformerJsonString (39.29s)
--- PASS: TestAccAWSCloudWatchEventTarget_kinesis (66.50s)
--- PASS: TestAccAWSCloudWatchEventTarget_sqs (22.96s)
--- PASS: TestAccAWSCloudWatchEventTarget_ssmDocument (27.00s)

[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!