resource/aws_launch_configuration: Clean up code

[radeksimko]

This is just a first step in bigger refactoring of the Launch Configuration resource with the aim to unblock #2132

[tombuildsstuff]

LGTM 👍

[Zordrak]

Per #2973 (comment) I am very concerned that it is no longer possible to specify the user_data attribute of a launch configuration without also providing a value. This prevents user_data from being conditionally specified in a module unless a non-zero default is specified; however changing the default will not only force a recreation of all launch configurations without userdata, but it also removes a perfectly valid AWS configuration from being supported by terraform unless you omit the user_data parameter. Since terraform does not and cannot support the conditional presence of parameters, it completely relies on the ability to detect an empty string as a null value where the parameter is optional in the API call.

[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!