Handle duplicate mesh file names in the conversion tool

[eholum-nasa]

We have simulations that are running multiple types of UR arms (ur5e + ur10e) which we want to use the conversion tool on. The problem is that UR has commonly named mesh files across their robots, https://github.com/UniversalRobots/Universal_Robots_ROS2_Description/tree/rolling/meshes, so when converting we end up with duplicated asset names and the output gets overwritten.

To get around this, we propose adding a suffix when duplicate mesh files are found. We just add _N and increment as needed. I'm not sure if there's a better way of handling this that would actually work in all cases (like somehow deduping based on file structure), so this is pretty simple and solves it if using the conversion script.

Updated and did a little clean up of the tools docs while I was at it. Sorry to nitpick about markdown formatting... The only thing that actually changed in the docs is adding a note about the added underscore, updating the lidar example since it was out of date, and changing a reference to use a relative path.

[eholum-nasa]

@esheetz-nasa tagging you here if you have the time to take a look?

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.66%. Comparing base (0ff1cfd) to head (b2c09f3).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #171   +/-   ##
=======================================
  Coverage   73.66%   73.66%           
=======================================
  Files          12       12           
  Lines        2761     2761           
  Branches      284      284           
=======================================
  Hits         2034     2034           
  Misses        608      608           
  Partials      119      119           

Flag	Coverage Δ
unittests	73.66% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.