Maureen Helm 38b4f1569e zephyr: Fix and rename stacks_analyze function in zephyr module.
Zephyr deprecated and then removed its stack_analyze function because it
was unsafe.  Use the new zephyr thread analyzer instead and rename the
MicroPython function to zephyr.thread_analyze() to be more consistent with
the implementation.

Tested on mimxrt1050_evk.

The output now looks like this:

>>> zephyr.thread_analyze()
Thread analyze:
 80004ff4            : unused 400 usage 112 / 512 (21 %)
 rx_workq            : unused 1320 usage 180 / 1500 (12 %)
 tx_workq            : unused 992 usage 208 / 1200 (17 %)
 net_mgmt            : unused 656 usage 112 / 768 (14 %)
 sysworkq            : unused 564 usage 460 / 1024 (44 %)
 idle                : unused 256 usage 64 / 320 (20 %)
 main                : unused 2952 usage 1784 / 4736 (37 %)
2020-06-12 10:24:01 +10:00
..