Clear up some of the logs

[doruphin]

When running simulations, there are a whole bunch of terminal messages that are either unneccessary or just straight up unaddressed errors, like

[gzserver-1] [Dbg] [gazebo_utils.cpp:67] added_mass: 
[gzserver-1]     6.15015   0.0668596    0.725079   0.0140736     0.80638   -0.519589
[gzserver-1]    0.235729     19.3015     1.90317   -0.602489   0.0293978  -0.0213517
[gzserver-1]   0.0118428    0.197162     32.1523     1.73426  -0.0857727    0.170258
[gzserver-1]  -0.0237789   -0.764146     1.81954    0.541859 -0.00732747   0.0146238
[gzserver-1]     0.66583  -0.0209113    -0.12233 -0.00613007    0.303522  -0.0405788
[gzserver-1]   -0.586397   0.0809334   -0.119217 -0.00848712  -0.0796626    0.429239

[krish-134]

Hey guys, I made some changes to make Gazebo launches a little cleaner in the terminal logs.

Issue:
gazebo_launch.py had verbose: 'true' hardcoded for gzserver, which enabled Gazebo terminal logging.
Combined with gazebo_utils.cpp/.hpp unconditionally logging every SDF parameter it read (including matrices for added_mass, linear_damping, etc.), this flooded the terminal on every simulation startup.

Changes:

• src/steelhead_gazebo/launch/gazebo_launch.py: verbose is now a proper DeclareLaunchArgument defaulting to false, instead of being hardcoded true. Pass verbose:=true if you need it back for debugging.
• src/steelhead_gazebo/gazebo_utils/include/gazebo_utils.hpp and .../src/gazebo_utils.cpp: switched the from gzdbg to gzlog on success. This means even with verbose:=true, those matrix/vector dumps should go to Gazebo's log file instead of your terminal.
• src/steelhead_gazebo/README.md — added a "Debugging / Verbose Logging" section documenting the verbose:=true flag and where to find the gzserver log (~/.gazebo/server-/default.log) if you need those parameter dumps later.

Let me know what you think!