AoC Issue: `list.fold` needs tail recursion optimization in JVM backend

[fridis]

This small test

fold_test is

  n := (0..100000).fold i32.type.sum
  say n

results in a stack overflow

 > $FUZION/bin/fz fold_test.fz  2>&1 | head -n 20

error 1: java.lang.StackOverflowError
	at fzC_2lteq_i32.fzRoutine(Unknown Source)
	at fzC_2infix_gt_i32.fzRoutine(Unknown Source)
	at fzC_1i32__1overflow_on_add.fzRoutine(Unknown Source)
	at fzC_1i32__1infix_plus.fzPrecondition(Unknown Source)
	at fzC_1i32__1infix_plus.fzPreconditionAndRoutine(Unknown Source)
	at fzC_i32_INTERN_type_i32__sum__2infix__U2219_.fzRoutine(Unknown Source)
	at fzC_i32_INTERN_type_i32__sum__2op.fzRoutine(Unknown Source)
	at fzC_list_i32__2fold.fzRoutine(Unknown Source)
	at fzC_list_i32__2fold.fzRoutine(Unknown Source)
	at fzC_list_i32__2fold.fzRoutine(Unknown Source)
	at fzC_list_i32__2fold.fzRoutine(Unknown Source)
	at fzC_list_i32__2fold.fzRoutine(Unknown Source)
	at fzC_list_i32__2fold.fzRoutine(Unknown Source)
	at fzC_list_i32__2fold.fzRoutine(Unknown Source)
	at fzC_list_i32__2fold.fzRoutine(Unknown Source)
	at fzC_list_i32__2fold.fzRoutine(Unknown Source)
	at fzC_list_i32__2fold.fzRoutine(Unknown Source)
	at fzC_list_i32__2fold.fzRoutine(Unknown Source)

The problem is that the recursive call in fold is not recognized as a tail recursion, probably because the result is first assigned to an expression result field before that is copied to the feature results field that is returned.