support pushing only `custom` resources with `amplify push custom`

### Is this feature request related to a new or existing Amplify category?

_No response_

### Is this related to another service?

_No response_

### Describe the feature you'd like to request

n/a

### Describe the solution you'd like

support pushing custom resources only with `amplify push custom`, which would be similar to `amplify push function` where we are able to push only "Function" resources, or specify a specific function

### Describe alternatives you've considered

```
amplify push custom [resource-names...]
```

### Additional context

_No response_

### Is this something that you'd be interested in working on?

- [ ] 👋 I may be able to implement this feature request

### Would this feature include a breaking change?

- [ ] ⚠️ This feature might incur a breaking change