Support setting heightmap position through sdf

[iche033]

🦟 Bug fix

Setting the heightmap sdf element has no effect. This PR reads the value from SDF DOM and passes it to ign-rendering so we can change the heightmap position offset.

Test by downloading a heightmap model from fuel, e.g.
https://app.ignitionrobotics.org/chapulina/fuel/models/Heightmap%20Bowl

edit the model.sdf in the fuel cache and set the values to anything other than 0 0 0 to change its position

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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[codecov]

Codecov Report

Merging #1054 (dffaa74) into main (f4d47b5) will increase coverage by 0.30%.
The diff coverage is 5.88%.

❗ Current head dffaa74 differs from pull request most recent head 35eb8da. Consider uploading reports for the commit 35eb8da to get more accurate results

@@            Coverage Diff             @@
##             main    #1054      +/-   ##
==========================================
+ Coverage   63.71%   64.01%   +0.30%     
==========================================
  Files         257      255       -2     
  Lines       20064    19917     -147     
==========================================
- Hits        12783    12750      -33     
+ Misses       7281     7167     -114     

Impacted Files	Coverage Δ
...ins/entity_context_menu/EntityContextMenuPlugin.cc	41.17% <0.00%> (ø)
src/gui/plugins/select_entities/SelectEntities.cc	10.04% <0.00%> (ø)
src/gui/plugins/spawn/Spawn.cc	10.25% <0.00%> (ø)
.../gui/plugins/transform_control/TransformControl.cc	6.97% <0.00%> (ø)
...lization_capabilities/VisualizationCapabilities.cc	7.96% <0.00%> (ø)
src/rendering/SceneManager.cc	28.74% <0.00%> (-0.03%)	⬇️
src/ServerConfig.cc	90.33% <100.00%> (ø)
src/gui/Gui.cc	64.34% <100.00%> (ø)
src/EntityComponentManager.cc	84.95% <0.00%> (-0.15%)	⬇️
src/gui/plugins/view_angle/ViewAngle.cc
... and 1 more

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