digital/io-hub/src/common-cc/path.cc: better way to handle the escape factor
digital/io-hub/src/common-cc/path.cc: add asserts
digital/io-hub/src/common-cc/path.cc: clean up the endpoints index enum

1. move enum about endpoints index
2. add nb of endpoints constant in the enum
3. use the enum constant instead of hard-coded index
4. change next_node type to match astar structure
digital/io-hub/src/common-cc/path.cc: use macro PATH_VECT_EQUAL when needed
digital/io-hub/src/common-cc: remove one navigation point around the cake

And clean up the declaration for better understanding, since half of the
navigation points around the cake are out of the playground.
digital/io-hub/src/common-cc/path: reduce the number of navigation points around the obstacles

On the second navigation points layer, this number is divided by 2.
More points seems unnecessary.
digital/io-hub/src/common-cc/path: clarify the clearance margins applied around obstacles
digital/io-hub/src/common-cc/path: prevent a possible overflow about navpoints weights

Also increase the weight of navpoints around the first layer to tend to avoid them.
digital/io-hub/src/common-cc/path: rename variable i into next_point for clearness