fix: Don't create a launch template if a custom one is used

[alexandre-bordiere]

Description

Motivation and Context

If use_custom_launch_template is set to true, then the module should not attempt to create a launch template regardless if the create_launch_template is also true.

Breaking Changes

N/A

How Has This Been Tested?

• [ ] I have updated at least one of the examples/* to demonstrate and validate my change(s)
• [x] I have tested and validated these changes using one or more of the provided examples/* projects
• [x] I have executed pre-commit run -a on my pull request

I am note sure if I need to update one of the examples but I did test locally and we can see that the plan is going from 83 resources to add to 82:

Before

After

Another way to see the result is in the outputs: The launch_template_id and other properties are null because the module is not creating the resource anymore.

Before

After