Draft: Convert rendering code to use OpenGL ES (Attempt 2)

Tarek Yasserrequested to merge
opengl_es_compilation_attempt_2 into develop

This MR is made following feedback from !598 (closed) and our weekly meetings. It covers 3 main points:

  1. Converting OpenGL 4.5 API calls to the equivalent-ish OpenGL ES 3.2 API calls
  2. Changing the used version directive and adding precision directives to shaders
  3. Removing uniform initializations from shaders + the gamma fix for texture fragment shaders

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