Added Loopback Simulator Package

[smitdumore]

---

Basic Info

Info	Please fill out this column
Ticket(s) this addresses	#3924
Primary OS tested on	Ubuntu 20.04.4
Robotic platform tested on	Rviz
Does this PR contain AI generated software?	No

---

Description of contribution in a few bullet points

• This new package serves as a Gazebo replacement.
• Designed for testing robot behaviors without the need for a complicated simulator.
• Uses incoming velocity commands to forward simulate the robot pose.
• A map is needed for navigation. The Robot can be spawned anywhere for repetative tests.

Description of documentation updates required from your changes

• A detailed readme is required for the nav2_loopback_sim package.

---

Future work that may be required in bullet points

• Needs to be tested for various robot platforms and scenarios.
• Needs some nice to have features.

For Maintainers:

• [ ] Check that any new parameters added are updated in navigation.ros.org
• [ ] Check that any significant change is added to the migration guide
• [ ] Check that any new features OR changes to existing behaviors are reflected in the tuning guide
• [ ] Check that any new functions have Doxygen added
• [ ] Check that any new features have test coverage
• [ ] Check that any new plugins is added to the plugins page
• [ ] If BT Node, Additionally: add to BT's XML index of nodes for groot, BT package's readme table, and BT library lists