gles: Define a `TextureShaderElement` #4663

Job	Run time
smithay-check-features	1m 16s
clippy-check	1m 33s
format	7s
check-msrv	0s
smithay-tests	0s
check-minimal	0s
anvil-check-features	0s
Documentation on Github Pages	0s
smallvil-check	0s
WLCS: ${{ matrix.job_name }}	0s
	2m 56s

Provide feedback