mesa/compiler: rework tear down of builtin/types

The issue we're running into when running CTS is that glsl types are
deleted while builtins depending on them are not.

This happens because on one hand we have glsl types ref counted, but
builtins are not. Instead builtins are destroyed when unloading libGL
or explicitly calling glReleaseShaderCompiler().

This change removes almost entirely any dealing with glsl types
ref/unref by letting the builtins deal with it instead. In turn we
introduce a builtin ref count mechanism. Each GL context takes a
reference on the builtins when compiling a shader for the first time.
It releases the reference when the context is destroyed. It can also
explicitly release those when glReleaseShaderCompiler() is called.

Finally we also take a reference on the glsl types when loading libGL
to avoid recreating glsl types too often.

v2: Ensure we take a reference if we don't have one in link step (Lionel)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110796
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>

src/mesa/state_tracker/st_context.c

@@ -1036,11 +1036,6 @@ st_destroy_context(struct st_context *st)
    st_destroy_context_priv(st, true);
    st = NULL;
 
-   /* This must be called after st_destroy_context_priv() to avoid a race
-    * condition between any shader compiler threads and context destruction.
-    */
-   _mesa_destroy_shader_compiler_types();
-
    free(ctx);
 
    if (save_ctx == ctx) {