nir/builder: Add a name format arg to nir_builder_init_simple_shader().

This cleans up a bunch of gross sprintfs and keeps the caller from needing
to remember to ralloc_strdup.  I added a couple of '"%s", name ? name :
""' to radv where I didn't fully trace through whether a non-null name was
being passed in.

I also took the liberty of adding a basic name to a few shaders (pan_blit,
unit tests)

Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7323>

src/compiler/nir/tests/builder_tests.cpp

@@ -75,7 +75,7 @@ nir_builder_test::nir_builder_test()
    glsl_type_singleton_init_or_ref();
 
    static const nir_shader_compiler_options options = { };
-   _b = nir_builder_init_simple_shader(MESA_SHADER_COMPUTE, &options);
+   _b = nir_builder_init_simple_shader(MESA_SHADER_COMPUTE, &options, "builder test");
    b = &_b;
 }