nir: Free liveness info when invalidating metadata

Liveness info can be huge, since with larger shaders it essentially
grows quadratically (linear increase in number of SSA defs *
linear increase in blocks).

Freeing liveness info early helps somewhat mitigate memory usage here.

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29577>

src/compiler/nir/nir_sweep.c

@@ -47,15 +47,6 @@ sweep_block(nir_shader *nir, nir_block *block)
 {
    ralloc_steal(nir, block);
 
-   /* sweep_impl will mark all metadata invalid.  We can safely release all of
-    * this here.
-    */
-   ralloc_free(block->live_in);
-   block->live_in = NULL;
-
-   ralloc_free(block->live_out);
-   block->live_out = NULL;
-
    nir_foreach_instr(instr, block) {
       gc_mark_live(nir->gctx, instr);