glsl/linker: location aliasing requires types to have the same width

From the OpenGL 4.60.5 spec, section 4.4.1 Input Layout Qualifiers,
Page 67, (Location aliasing):

  " Further, when location aliasing, the aliases sharing the location
    must have the same underlying numerical type and bit
    width (floating-point or integer, 32-bit versus 64-bit, etc.) and
    the same auxiliary storage and interpolation qualification."

Additionally, we have improved the linker error descriptions.
Specifically, when taking structs into account we were producing a
linker error because we assumed that all components in each location
were used and that would cause component aliasing. This is not
accurate of the actual problem. Now, the failure specifies that the
underlying numerical type incompatibility is the cause for the
failure.

Fixes the following piglit test:

tests/spec/arb_enhanced_layouts/linker/component-layout/vs-to-fs-width-mismatch-double-float.shader_test

v2:
  - Do not assert if we see invalid numerical types. These come
    straight from shader code, so we should produce linker errors if
    shaders attempt to do location aliasing on variables that are not
    numerical such as records.
  - While we are at it, improve error reporting for the case of
    numerical type mismatch to include the shader stage.

v3:
  - Allow location aliasing of images and samplers. If we get these
    it means bindless support is active and they should be handled
    as 64-bit integers (Ilia)
  - Make sure we produce link errors for any non-numerical type
    for which we attempt location aliasing, not just structs.

v4:
  - Rebased with minor fixes (Andres).
  - Added fixing tag to the commit log (Andres).

v5:
  - Remove the helper function and check individually for the
    underlying numerical type and bit width (Timothy).
  - Implicitly, assume that any non-treated type which is checked for
    its underlying numerical type is either integer or
    float and has a defined bit width (Timothy).
  - Implicitly, assume that structs are the only non-treated
    non-numerical type (Timothy).
  - Improve the linker error descriptions and commit log (Andres).

Fixes: 13652e75 ("glsl/linker: Fix type checks for location aliasing")
Cc: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: Timothy Arceri <tarceri@itsqueeze.com>
Cc: Iago Toral Quiroga <itoral@igalia.com>
Signed-off-by: Andres Gomez <agomez@igalia.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
(cherry picked from commit 75a3dd97)
[Andres Gomez: is_record() instead of is_struct() and brought glsl_base_type_get_bit_size]
Signed-off-by: Andres Gomez <agomez@igalia.com>