move commsec-test from apps to src/gcs
rename 'smaccmpilot-shared' package to 'smaccm-shared-comm'
flight: changes for smaccm-shared-comm
smaccm-mavlink generator: changes for smaccm-comm-shared
smaccm-mavlink generator: impl changes

* add handy regen script
* regen targets from gcs/mavlink submodule's message defs
* reject messages with wire length over 80
smaccm-mavlink: regenerate with newest generator
smaccm-mavlink: fix sender for smaccm-comm-shared