Split up functions in liverange.rs

This helps with profiling even if they are inlined since perf with DWARF
callgraph profiling can attribute execution time to inlined functions.

src/ion/mod.rs

@@ -92,6 +92,8 @@ impl<'a, F: Function> Env<'a, F> {
     pub(crate) fn init(&mut self) -> Result<(), RegAllocError> {
         self.create_pregs_and_vregs();
         self.compute_liveness()?;
+        self.build_liveranges();
+        self.fixup_multi_fixed_vregs();
         self.merge_vreg_bundles();
         self.queue_bundles();
         if log::log_enabled!(log::Level::Trace) {