COMPMID-3979 Sanitise Padding Removal epic

COMPMID-3979 Sanitise Padding Removal epic

* Add missing padding immutability asserts in all relevant CL kernels
* Remove unnecessary zero padding validation tests.

Change-Id: If93f9ccbc988e0286f5e7b135f812141476d5da0
Signed-off-by: SiCong Li <sicong.li@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/4446
Reviewed-by: Gian Marco Iodice <gianmarco.iodice@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>