Remove/Modify auto-generation of config.yaml in empty directory

**Describe the bug**
When tk8 is run in a directory which does not have `config.yaml`, it tries to auto generate it by saying:
```
No default config was provided. Generating one for you.
```

The auto-generated `config.yaml` is only usable for aws provisioner and not for others.

**To Reproduce**
Steps to reproduce the behavior:
1. Download `tk8` binary in empty folder.
2. Setup cattle-aws cluster without `config.yaml`: `tk8 cluster install cattle-aws`

**Expected behavior**
We have two options in this case:

1. Instead of auto-generating `config.yaml`, we should tell the user to create the `config.yaml` before running the command since we cannot generate multiple configs for multiple provisioners.

2. Implement the code for mapping between different `config.yaml`'s for different provisioners.

Start with the `tk8 cluster install cattle-aws` entry point and trace where a missing `config.yaml` is auto-generated; the payload names no source file or test. Resolve whether the command should require a user-created config or support provisioner-specific mappings, then verify behavior for an empty directory and non-AWS provisioners.

Written by the indexing model from the issue text.