[macOS] modify definition of bufferFetch1 to work when GL_ARB_texture_buffer_range is not available

[srmainwaring]

This PR modifies the shader piece CrossPlatformSettings_piece_all.glsl to work when the OpenGL extension GL_ARB_texture_buffer_range is not available.

The definition of bufferFetch1 was failing for OpenGL < 4.2 resulting in compile errors for lighting shaders

🦟 Bug fix

Partial fix of #422

Summary

This is a single line change to the cross platform settings shader piece. It changes the definition of bufferFetch1 to use the bufferFetch definition which has compatibility settings rather than use texelFetch directly.

Before this change the shaders would fail to compile using the ogre2 render engine on macOS. After this change the shaders will compile.

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)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Not all tests pass on macOS. The failures are listed below, but are not connected to the changes in this PR.

The following tests FAILED:
	  7 - UNIT_COMVisual_TEST (Subprocess aborted)
	 19 - UNIT_Heightmap_TEST (SEGFAULT)
	 59 - UNIT_RenderingIface_TEST (SEGFAULT)
	 83 - INTEGRATION_depth_camera (Failed)

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[codecov]

Codecov Report

Merging #462 (5aceaf2) into ign-rendering6 (67b5420) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@                Coverage Diff                 @@
##           ign-rendering6     #462      +/-   ##
==================================================
- Coverage           53.49%   53.49%   -0.01%     
==================================================
  Files                 192      192              
  Lines               19560    19560              
==================================================
- Hits                10464    10463       -1     
- Misses               9096     9097       +1     

Impacted Files	Coverage Δ
...e/ignition/rendering/base/BaseGaussianNoisePass.hh	96.66% <0.00%> (-3.34%)	⬇️

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[iche033]

looks good to me.