Added gripper GetKinematics

[gabegottlob]

1. Added abstract method in gripper.py
2. Implemented GetKinematics in service.py
3. Implemented get_kinematics in client.py
4. Updated test_gripper with new tests (and added get_kinematics to the mock gripper)

[github-actions]

Warning your change may break code samples. If your change modifies any of the following functions please contact @viamrobotics/fleet-management. Thanks!

component	function
base	is_moving
board	gpio_pin_by_name
camera	get_image
encoder	get_position
motor	is_moving
sensor	get_readings
servo	get_position
switch	get_position
arm	get_end_position
gantry	get_lengths
gripper	is_moving
movement_sensor	get_linear_acceleration
input_controller	get_controls
audio	get_properties
pose_tracker	get_poses
power_sensor	get_power
motion	get_pose
vision	get_properties
mlmodel	metadata
slam	get_point_cloud_map

[stuqdog]

lgtm!