[backport] -d:danger should imply -d:release (#13336)

(cherry picked from commit c6d5f0df8d)

config/nim.cfg

@@ -76,6 +76,7 @@ path="$lib/pure"
   debugger:off
   line_dir:off
   opt:speed
+  define:release
 @end
 
 @if false: # not danger: # this does not work yet.

tests/misc/tdangerisrelease.nim

@@ -0,0 +1,13 @@
+discard """
+  cmd: "nim c -d:danger -r $file"
+  output: '''
+a
+b
+c
+'''
+"""
+
+echo "a"
+when defined(release):
+  echo "b"
+echo "c"