Revert all the vertex pack specific commits (lightgrid changes)

Revert "Remove last remaining uses of the lightdirection attribute."

This reverts commit e70632fee91aedbf0567014ee41659f31ecc5f37.

Revert "Remove unused AmbientLight and DirectedLight attributes."

This reverts commit 7fa1e5cc5c8a18aaf72f4b69d11a2e79502e823f.

Revert "Add light grid shading to the vertexLighting_DBS_world shader."

This reverts commit 1472573a2a7825a683187c327af75e40bc4e6b11.

Revert "Remove unused light uniforms from vertexLighting_DBS_entity shader"

This reverts commit 6cc09fbae61dae53825fe1fa6f212bb49a4eeb7d.

Revert "Add light grid sampling to the vertexLighting_DBS_entity shader."

This reverts commit 550682bd3013cc8f9a82eda7756be795781a8db4.

Conflicts:
	src/engine/renderer/gl_shader.h

Revert "Upload light grid to 3D textures."

This reverts commit 77d8ef867ca776189c0ca6c67a541751f6f0d7d6.

Revert "Pack gridPoint struct into 2 * 4 bytes."

This reverts commit cb56f821d1d9fa82905c58891bb8008f5ce80f2e.

Revert "Remove origin vector from gridPoint struct."

This reverts commit c093e76737580254c1df34a472f250f49db65e2a.

Revert "Remove support for paintColor attribute."

This reverts commit ed7ee07c1a9a285b106f1d552426aceccbbcdf91.