🐛 Our python datahub search client does not return correct page search results

[LavMatt]

Describe the bug.

The start parameter in the graphql query of our search client's search method, had until now assumed to be start page and passing a page number would return the results of size count from that page.

start actually refers to the index of individial serach results so to get page would be

"start": count * page,

need to implement the fix in the catalogue package.

This bug is presenting itself in the paginated results of find-moj-data

To Reproduce

1. make a search with more than 20 results
2. got to page 2
3. see top result is 2nd from top result from previous page

Expected Behaviour

subsequent pages of search results display unique results. Should match the page results as seen in datahub UI

Additional context

No response