nir/spirv: add gl_spirv_validation method

nir/spirv: add gl_spirv_validation method

ARB_gl_spirv adds the ability to use SPIR-V binaries, and a new
method, glSpecializeShader. Here we add a new function to do the
validation for this function:

From OpenGL 4.6 spec, section 7.2.1"

   "Shader Specialization", error table:

    INVALID_VALUE is generated if <pEntryPoint> does not name a valid
    entry point for <shader>.

    INVALID_VALUE is generated if any element of <pConstantIndex>
    refers to a specialization constant that does not exist in the
    shader module contained in <shader>.""

v2: rebase update (spirv_to_nir options added, changes on the warning
    logging, and others)

v3: include passing options on common initialization, doesn't call
    setjmp on common_initialization

v4: (after Jason comments):
  * Rename common_initialization to vtn_builder_create
  * Move validation method and their helpers to own source file.
  * Create own handle_constant_decoration_cb instead of reuse existing one

v5: put vtn_build_create refactoring to their own patch (Jason)

v6: update after vtn_builder_create method renamed, add explanatory
    comment, tweak existing comment and commit message (Timothy)