Add a function to list out all the available phenotypic filters 

At the moment only for few terms works in `cb_search_phenotypic_filters()` 

```R
cb_search_phenotypic_filters(cloudos = my_cloudos, term = "cancer")
```

- [ ] Change the arg name from `term` -> `phenotype` (take a vote on this)
- [ ] Make a function to list out all the available phenotypic filters, so a user no need to search and can directly take the phenotypic filters id to next step.