title: BigQuery GROUP_CONCAT drops precision of float numbers
body: <p>I use GROUP_CONCAT to concatenate a list of float numbers, but the results drop the precision and only preseves 4 decimals.
  How can I group_concat the number with original precision?</p>
  
  <p>Example, 
  GROUP_CONCAT trim the float number 49.2795576 to '49.2796'</p>