simulation organization and cleanup

- new modules/simulation directory to collect all simulators and related modules
 - new Tools/simulation directory to collect and organize scattered simulation submodules, scripts, etc
 - simulation module renamed to simulator_mavlink
 - sih renamed to simulator_sih (not a great name, but I wanted to be clear it was a simulator)
 - ignition_simulator renamed to simulator_ignition_bridge
 - large sitl_target.cmake split by simulation option and in some cases pushed to appropriate modules
 - sitl targets broken down to what's actually available (eg jmavsim only has 1 model and 1 world)
 - new Gazebo consistently referred to as Ignition for now (probably the least confusing thing until we fully drop Gazebo classic support someday)

.gitmodules

@@ -6,12 +6,12 @@
 	path = src/drivers/uavcan/libuavcan
 	url = https://github.com/dronecan/libuavcan.git
 	branch = main
-[submodule "Tools/jMAVSim"]
-	path = Tools/jMAVSim
+[submodule "Tools/simulation/jmavsim/jMAVSim"]
+	path = Tools/simulation/jmavsim/jMAVSim
 	url = https://github.com/PX4/jMAVSim.git
 	branch = master
-[submodule "Tools/sitl_gazebo"]
-	path = Tools/sitl_gazebo
+[submodule "Tools/simulation/gazebo/sitl_gazebo"]
+	path = Tools/simulation/gazebo/sitl_gazebo
 	url = https://github.com/PX4/PX4-SITL_gazebo.git
 	branch = master
 [submodule "src/drivers/gps/devices"]
@@ -31,10 +31,10 @@
 	url = https://github.com/PX4/NuttX-apps.git
 	branch = px4_firmware_nuttx-10.1.0+
 [submodule "Tools/flightgear_bridge"]
-	path = Tools/flightgear_bridge
+	path = Tools/simulation/flightgear/flightgear_bridge
 	url = https://github.com/PX4/PX4-FlightGear-Bridge.git
-[submodule "Tools/jsbsim_bridge"]
-	path = Tools/jsbsim_bridge
+[submodule "Tools/simulation/jsbsim/jsbsim_bridge"]
+	path = Tools/simulation/jsbsim/jsbsim_bridge
 	url = https://github.com/PX4/px4-jsbsim-bridge.git
 [submodule "src/drivers/cyphal/libcanard"]
 	path = src/drivers/cyphal/libcanard