Proposal for `fuelup` to detect and warn the user if there is an old version of `fuel-core` running in the background, when `fuel-core` is updated

### Problem you are trying to solve

The other day I spent quite a bit of time banging my head against the keyboard trying to figure out why, despite upgrading `fuel-core`, I was getting an error message that should only have been possible if I had been using an outdated version. It turns out that I had an orphaned `fuel-core` process running the background on my machine.

### Solution you'd like

I'd like `fuelup` to detect and warn the user if there is an old version of `fuel-core` running in the background, when `fuel-core` is updated, to prevent the issue above from happening in the future!

### Notes

_No response_