cmd/compile: change Func.{Dcl,Inldcl} from NodeList to slice
A slice uses less memory than a NodeList, and has better memory locality
when walking the list.
This uncovered a tricky case involving closures: the escape analysis
pass when run on a closure was appending to the Dcl list of the OCLOSURE
rather than the ODCLFUNC. This happened to work because they shared the
same NodeList. Fixed with a change to addrescapes, and a check to
Tempname to catch any recurrences.
This removes the last use of the listsort function outside of tests.
I'll send a separate CL to remove it.
Unfortunately, while this passes all tests, it does not pass toolstash
-cmp. The problem is that cmpstackvarlt does not fully determine the
sort order, and the change from listsort to sort.Sort, while generally
desirable, produces a different ordering. I could stage this by first
making cmpstackvarlt fully determined, but no matter what toolstash -cmp
is going to break at some point.