nir/linker: fill up uniform_storage with explicit data

nir/linker: fill up uniform_storage with explicit data

Specifically, offset, stride (coming from arrays or matrices) and
row_major.

On GLSL, most of that info is computed using the layout qualifier, but
on ARB_gl_spirv they are explicit, and for Mesa, included on the
glsl_type.

From ARB_gl_spirv spec:

   "Mapping of layouts

      std140/std430 -> explicit *Offset*, *ArrayStride*, and
                       *MatrixStride* Decoration on struct members""

    "7.6.2.spv SPIR-V Uniform Offsets and Strides

    The SPIR-V decorations *GLSLShared* or *GLSLPacked* must not be
    used. A variable in the *Uniform* Storage Class decorated as a
    *Block* must be explicitly laid out using the *Offset*,
    *ArrayStride*, and *MatrixStride* decorations"

For offset we needed to include the parent and index_in_parent while
processing the type, as the offset is maintained on glsl_struct_field
of the parent type, not on the type itself.

v2: Fix the default values for MATRIX_STRIDE, ARRAY_STRIDE and
    ROW_MAJOR when the variable is not backed by a buffer object
    (Antia Puentes).

v3: Update after Jason series "SPIR-V: Use NIR deref instructions for
    UBO/SSBO access" that included just one explicit stride, instead
    of a previous patch we wrote that had matrix_stride and
    array_stride (Alejandro)

Signed-off-by: Antia Puentes <apuentes@igalia.com>
Signed-off-by: Alejandro Piñeiro <apinheiro@igalia.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>