Krishna/clear logs

[krish-134]

Repeated message from Issues:

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!