First version - just make sure all heaps sweep rather than compact if special_sweep_p is set by one heap. (#69177)

The issue was that in SVR GC, some GC threads would not be able to obtain a region for gen 0, and thus set special_sweep_p, but later on, this setting would be ignored when GC threads voted whether to sweep or compact. So we ended up compacting anyway, not getting a gen 0 region for some heaps, and verify_regions failing.

Fix is simply to always do sweep when special_sweep_p is set.

This still doesn't make ASP.NET work with tight hard limits - more work is needed.

Author: PeterSolMS

src/coreclr/gc/gc.cpp

@@ -29428,6 +29428,13 @@ void gc_heap::plan_phase (int condemned_gen_number)
 
             for (i = 0; i < n_heaps; i++)
             {
+#ifdef USE_REGIONS
+                if (special_sweep_p)
+                {
+                    g_heaps[i]->gc_policy = policy_sweep;
+                }
+                else
+#endif //USE_REGIONS
                 if (pol_max > g_heaps[i]->gc_policy)
                     g_heaps[i]->gc_policy = pol_max;
 #ifndef USE_REGIONS