patch 8.2.2124: Vim9: a range cannot be computed at runtime

Problem:    Vim9: a range cannot be computed at runtime.
Solution:   Add the ISN_RANGE instruction.
diff --git a/src/testdir/test_vim9_cmd.vim b/src/testdir/test_vim9_cmd.vim
index 37fc559..1986c0f 100644
--- a/src/testdir/test_vim9_cmd.vim
+++ b/src/testdir/test_vim9_cmd.vim
@@ -614,6 +614,17 @@
   assert_equal('above', getline(3))
   assert_equal('below', getline(4))
 
+  # compute range at runtime
+  setline(1, range(1, 8))
+  @a = 'aaa'
+  :$-2put a
+  assert_equal('aaa', getline(7))
+
+  setline(1, range(1, 8))
+  :2
+  :+2put! a
+  assert_equal('aaa', getline(4))
+
   bwipe!
 enddef