The current pull=Pin.PULL_HOLD argument doesn't make a lot of sense in the
context of what it actually does vs what the ESP32 quickref document says
it does.
This commit removes PULL_HOLD and adds a new hold=True|False keyword
argument to Pin()/Pin.init(). Setting this to True will cause the ESP32 to
lock the configuration of the pin – including direction, output value,
drive strength, pull-up/-down – such that it can't be accidentally changed
and will be retained through a watchdog or internal reset.
Fixes issue #8283, and see also #8284.
7684c996bc