WorkWrap: Use SysLocal Name for Thunk Splitting (#19180)
Since !4493 (closed) we annotate top-level bindings with demands, which leads to novel opportunities for thunk splitting absent top-level thunks.
It turns out that thunk splitting wasn't quite equipped for that,
because it re-used top-level, External
Names for local helper Ids.
That triggered a CoreLint error (#19180 (closed)), reproducible with T19180
.
Fixed by adjusting the thunk splitting code to produce SysLocal
names
for the local bindings.
Fixes #19180 (closed).