Bluetooth: Break add adv into two mgmt commands

This patch adds support for the new advertising add interface, with the
first command setting advertising parameters and the second to set
advertising data. The set parameters command allows the caller to leave
some fields "unset", with a params bitfield defining which params were
purposefully set. Unset parameters will be given defaults when calling
hci_add_adv_instance. The data passed to the param mgmt command is
allowed to be flexible, so in the future if bluetoothd passes a larger
structure with new params, the mgmt command will ignore the unknown
members at the end.

This change has been validated on both hatch (extended advertising) and
kukui (no extended advertising) chromebooks running bluetoothd that
support this new interface. I ran the following manual tests:
- Set several (3) advertisements using modified test_advertisement.py
- For each, validate correct data and parameters in btmon trace
- Verified both for software rotation and extended adv

Automatic test suite also run, testing many (25) scenarios of single and
multi-advertising for data/parameter correctness.

Reviewed-by: Sonny Sasaka <sonnysasaka@chromium.org>
Signed-off-by: Daniel Winkler <danielwinkler@google.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>