Improve performance of landing page

[ciyer]

Description

The following changes should be made to the data retrieved for the landing page:

• Just get 5 projects for the landing page
• Just get project name/namespace for the quick-nav use (see just-names query below)

Follow-up to #1505.

Details

minimal query

{
  projects(membership: true, first: 100) {
    pageInfo {
      startCursor
      endCursor
    }
    nodes {
      avatarUrl
      description
      name
      namespace {
        fullPath
      }
      path
      lastActivityAt
      tagList
    }
  }
}

just names query

{
  projects(membership: true, first: 100) {
    pageInfo {
      startCursor
      endCursor
    }
    nodes {
      name
      namespace {
        fullPath
      }
      path
    }
  }
}