Fix exception tracking in try blocks (#10455)

Exceptions raised inside a nkFinally/nkExcept block are not caught by
the block itself.

Fixes #3886

tests/effects/teffects7.nim

@@ -0,0 +1,14 @@
+discard """
+  errormsg: "can raise an unlisted exception: ref FloatingPointError"
+  line: 10
+"""
+
+proc foo() {.raises: [].} =
+  try:
+    discard
+  except KeyError:
+    raise newException(FloatingPointError, "foo")
+  except Exception:
+    discard
+
+foo()