Declare and import params

[aalbaali]

Description

Write a (templated) function that declares and imports ROS2 parameters.

That is, a function that replaces the following two lines

this->declare_parameter<double>("publisher_est_pose_freq", 10);
this->get_parameter("publisher_est_pose_freq", est_pose_pub_freq_);

This function is especially useful when declaring const variables

AC:

• Create function
• Test function, if possible (check ROS2 testing, which I haven't tried yet)
• Use the function whenever necessary in the code

[aalbaali]

Implemented already