Hash table header extension pages

[k2bd]

At the moment there's a limit to hash table size due to limited header page space to index block pages. A simple extension would be to allocate a byte of memory to the header page for an optional header extension page ID which would be structured like:

| Header page ID (4) | Previous extension page ID or null (4) | Next extension page ID or null (4) | Block page IDs (4084) |

And the header page would then look like:

| LSN (4) | Size (4) | PageId(4) | NextBlockIndex(4) | First extension page ID or null (4) | Block page IDs (4076) |