Auto merge of #24310 - ceyusa:clean-display-glutin, r=ferjm

Clean up gating and order of getting display/glcontext from glutin

This patch simply simplify the OS gating for getting display and gl
context from glutin since it is only used for a linux, mac and not
UWP-based windows.

Also, in linux tries to fetch the wayland display and don't rely
on EGLDisplay because it might bring problems in servo/media.
Nonetheless it is required to compile render-unix in servo-media
with feature 'gl-wayland'

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