Don't hang in createHistoryStream() when blocks are not available

[josephmturner]

createHistoryStream currently hangs when blocks are not available. I would like to iterate over the full history of a hyperbee which is not fully replicated. Could createHistoryStream() accept a { wait: false } argument to make it keeping loop when it encounters BLOCK_NOT_AVAILABLE? Perhaps this API could be used like this:

for await (const entry of db.createHistoryStream({ wait: false })) {
  if (entry.type = 'put') handlePut()
  if (entry.type = 'del') handleDel()
  if (entry.type = 'BLOCK_NOT_AVAILABLE') handleMissingBlock()
}