Implement optimization pass to remove `__anvill` switch intrinsics about anvill

[kumarak]

Attached specification include function with indirect control flow instruction and the target list. Anvill lift the complete list of targets with switch intrinsics:

...
991:                                              ; preds = %983
  %992 = zext i8 %984 to i32
  %993 = shl nuw nsw i32 %992, 2
  %994 = add i32 %993, add (i32 ptrtoint (i32* @var_835a000_i to i32), i32 -763272)
  %995 = inttoptr i32 %994 to i32*
  %996 = load i32, i32* %995, align 4
  %997 = add i32 %996, ptrtoint (i32* @var_835a000_i to i32)
  %998 = call i32 (i32, ...) @__anvill_complete_switch(i32 %997, i32 134522973, i32 136578775, i32 136578784, i32 136578793, i32 136578809, i32 136578818)
  %999 = add i32 %996, add (i32 ptrtoint (i32* @var_835a000_i to i32), i32 9)
  switch i32 %998, label %1000 [
    i32 0, label %449
    i32 1, label %1001
    i32 2, label %1004
    i32 3, label %1007
    i32 4, label %1010
    i32 5, label %1014
  ]

spec.json.zip

[pgoodman]

Done in #261.