fixed nim-lang/nimsuggest#82 pure enum field sug (#16676)

- previous code wasn't account for tyEnum being wrapped in tyTypeDesc
- now pure enum fields are suggested

nimsuggest/tests/tsug_enum.nim

@@ -0,0 +1,18 @@
+## suggestions for enums
+
+type
+  LogLevel {.pure.} = enum
+    debug, log, warn, error
+  
+  FooBar = enum
+    fbFoo, fbBar
+
+echo fbFoo, fbBar
+
+echo LogLevel.deb#[!]#
+
+discard """
+$nimsuggest --tester $file
+>sug $1
+sug;;skEnumField;;debug;;LogLevel;;*nimsuggest/tests/tsug_enum.nim;;5;;4;;"";;100;;Prefix
+"""