feat(aws): parameterize time_sleep duration with input wait_time

[dh11640]

Parameterize the create_duration parameter for time_sleep resources.

Closes #61

[afiune]

This change looks great, I have just two quick comments:

1. Set the default time to 10s
2. Add a quick documentation about this new input in the Inputs sectio of the README.md

[afiune]

Can we change the default to be 10s? I think we want to make increase the default so that others won't have to customize it that often.

[dh11640]

Done!

[dh11640]

Oops, missed the readme bit. Just pushed that as well

[afiune]

YESS!! Thank You!

[afiune]

Just upgraded our demo environment and ran a terraform apply and we see a few resources that will be destroyed since this change is replacing the time_sleep resources, users will see plan output similar to:

  # module.tech_ally_aws_config.module.lacework_cfg_iam_role.time_sleep.wait_5_seconds will be destroyed
  - resource "time_sleep" "wait_5_seconds" {
      - create_duration = "5s" -> null
      - id              = "2020-07-01T19:54:19Z" -> null
    }
  # module.tech_ally_aws_config.module.lacework_cfg_iam_role.time_sleep.wait_time will be created
  + resource "time_sleep" "wait_time" {
      + create_duration = "10s"
      + id              = (known after apply)
    }

Plan: 4 to add, 0 to change, 4 to destroy.

After applied the time resources were destroyed and the new ones took their place:

Apply complete! Resources: 4 added, 0 changed, 4 destroyed.