Add `all` to the Choco Source Remove command to remove all sources at once.

### Checklist

- [X] I have verified this is the correct repository for opening this issue.
- [X] I have verified no other issues exist related to my request.

### Is Your Feature Request Related To A Problem? Please describe.

We should add the ability to remove all sources with a simple command in case a customer wants to start from scratch with sources (for instance, if they change repositories.)

### Describe The Solution. Why is it needed?

Currently you have to know the name of each source to remove them as well as only being able to remove them one at at time.

### Additional Context

To be consistent with other Chocolatey CLI commands, `choco source remove all` would be better.

However, we need to remember that we cannot remove the `chocolatey.licensed` source, as it will be put back again the next time Chocolatey CLI is run. To preserve any settings on this source (for example, if it has been disabled) we should not remove that source at all. We should output a warning to indicate that we haven't removed that source, but it can be disabled with `choco source disable -n="'chocolatey.licensed'"`.

### Related Issues

- [Zendesk ticket for reference](https://chocolatey.zendesk.com/agent/tickets/18030)