environment_preload: fix windows compiler warnings

[scpeters]

🦟 Bug fix

Fixes some compiler warnings in windows CI from the environment_preload system

Summary

The garden windows CI build has no test failures and just a few compiler warnings:

• https://build.osrfoundation.org/view/ign-garden/job/ign_gazebo-gz-7-win/143/msbuild/fileName.1593292455/

This is an attempt to fix the compiler warnings in the environment_preload system, specifically VisualizationTool.cc:80.

'argument': conversion from 'double' to 'unsigned int', possible loss of data

From what I can see, the /environment/visualize/res topic uses a gz::msgs::Vector3d to store 3 integers because there is no gz::msgs::Vector3i. This PR casts the double values to unsigned int in the callback and changes the internal storage and APIs to use unsigned int instead of double.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

Attention: 9 lines in your changes are missing coverage. Please review.

Comparison is base (c73c12b) 64.74% compared to head (6f5e848) 64.73%.

❗ Current head 6f5e848 differs from pull request most recent head 1b7fdf0. Consider uploading reports for the commit 1b7fdf0 to get more accurate results

Files	Patch %	Lines
.../systems/environment_preload/EnvironmentPreload.cc	0.00%	6 Missing ⚠️
...c/systems/environment_preload/VisualizationTool.cc	0.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           gz-sim7    #2246      +/-   ##
===========================================
- Coverage    64.74%   64.73%   -0.01%     
===========================================
  Files          357      357              
  Lines        29138    29142       +4     
===========================================
+ Hits         18864    18865       +1     
- Misses       10274    10277       +3     

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[scpeters]

windows CI is now clean, but UNIT_Server_TEST flaked on gz_sim-ci-pr_any-focal-amd64

[arjo129]

LGTM! Thanks. Tested it and works as expected.