[BridgeJS] Pass String parameters unretained as (address, length)

[sliemeobn]

#677

[sliemeobn]

here are the results from the ElementaryUI benchmark:

pass retained (current BridgeJS):

  01_run1k                    200.46 ms
  02_replace1k                 538.8 ms
  03_update10th1k_x16          81.42 ms
  04_select1k                  13.35 ms
  05_swap1k                    28.29 ms
  06_remove-one-1k             20.09 ms
  08_create1k-after1k_x2      503.32 ms
  09_clear1k_x8                95.74 ms
  21_ready-memory               1.06 MB
  22_run-memory                 2.61 MB
  25_run-clear-memory           3.15 MB

pass unretained (this PR):

  01_run1k                      95.5 ms
  02_replace1k                205.06 ms
  03_update10th1k_x16          83.56 ms
  04_select1k                  13.01 ms
  05_swap1k                    28.21 ms
  06_remove-one-1k             19.41 ms
  08_create1k-after1k_x2      131.57 ms
  09_clear1k_x8                49.33 ms
  21_ready-memory               1.05 MB
  22_run-memory                 2.17 MB
  25_run-clear-memory           3.15 MB