listProjects return one page at a time. A page has the
items and, when more items follow, a nextPageToken. To get the next page, send
that token back as the pageToken query parameter. When a page has no
nextPageToken, it is the last one.
pageSize sets how many items a page holds, up to the limit the endpoint
documents; for listProjects it is 1 to 100. Each list endpoint’s parameters,
including its own filters, are in the API reference. The
clients do not page automatically, so you write the loop.