Handle pagination via next-page-token in REST Catalog (#1097)

## Which issue does this PR close?

- Closes #1096

## What changes are included in this PR?

Implements pagination on the `GET /v1/namespaces` and `GET
/v1/namespaces/my_namespace/tables` APIs by looking for a
`next-page-token` and adding a `pageToken` query parameter on the next
request with that token.

This is allowed on the Iceberg Catalog REST API spec: 
ListTablesResponse:
https://github.com/apache/iceberg/blob/main/open-api/rest-catalog-open-api.yaml#L3898
ListNamespacesResponse:
https://github.com/apache/iceberg/blob/main/open-api/rest-catalog-open-api.yaml#L3909

PageToken:
https://github.com/apache/iceberg/blob/main/open-api/rest-catalog-open-api.yaml#L2009C5-L2029C40
> PageToken:
>       description:
> An opaque token that allows clients to make use of pagination for list
APIs
> (e.g. ListTables). Clients may initiate the first paginated request by
sending an empty
>         query parameter `pageToken` to the server.
> Servers that support pagination should identify the `pageToken`
parameter and return a
> `next-page-token` in the response if there are more results available.
After the initial
> request, the value of `next-page-token` from each response must be
used as the `pageToken`
> parameter value for the next request. The server must return `null`
value for the
>         `next-page-token` in the last response.
> Servers that support pagination must return all results in a single
response with the value
> of `next-page-token` set to `null` if the query parameter `pageToken`
is not set in the
>         request.
> Servers that do not support pagination should ignore the `pageToken`
parameter and return
> all results in a single response. The `next-page-token` must be
omitted from the response.
> Clients must interpret either `null` or missing response value of
`next-page-token` as
>         the end of the listing results.

## Are these changes tested?

Yes, unit tests have been added to cover pagination with one page and
multiple pages for both APIs

Author: phillipleblanc