When glVertexAttribPointer is called with a type parameter that doesn't
match the vertex attribute binding's type in shader, the vulkan backend
used to force the stride to 0. This is acceptable since this usecase is
unspecified in spec.

To allow for better app compatibility, introduce a new extension that
requires normal glVertexAttribPointer functionality to be maintained if
the mismatched vertex attribute type is a mismatched integer type sign.

This change also modifies the VkFormat used when a mismatch in
signedness occurs to use a VkFormat with the same component width as
the type parameter.

Bug: angleproject:5762
Test: VertexAttributeTestES3.DrawWithRelaxedVertexAttributeType*
Test: VertexAttributeTestES3.DrawWithMismatchedComponentCount*
Change-Id: I7e5281500afc3d77f0775821447cabfad3ff2d66
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2765012
Commit-Queue: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>