intel/compiler/vec4: Switch liveness analysis to IR analysis framework

This involves wrapping vec4_live_variables in a BRW_ANALYSIS object
and hooking it up to invalidate_analysis() so it's properly
invalidated.  Seems like a lot of churn but it's fairly
straightforward.  The vec4_visitor invalidate_ and
calculate_live_intervals() methods are no longer necessary after this
change.

Reviewed-by: Matt Turner <mattst88@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4012>

src/intel/compiler/brw_vec4_reg_allocate.cpp

@@ -201,8 +201,7 @@ vec4_visitor::reg_allocate()
    if (0)
       return reg_allocate_trivial();
 
-   calculate_live_intervals();
-
+   const vec4_live_variables &live = live_analysis.require();
    int node_count = alloc.count;
    int first_payload_node = node_count;
    node_count += payload_reg_count;
@@ -215,7 +214,7 @@ vec4_visitor::reg_allocate()
       ra_set_node_class(g, i, compiler->vec4_reg_set.classes[size - 1]);
 
       for (unsigned j = 0; j < i; j++) {
-	 if (live_intervals->vgrfs_interfere(i, j)) {
+	 if (live.vgrfs_interfere(i, j)) {
 	    ra_add_node_interference(g, i, j);
 	 }
       }