base parseEnum on a case statement, fixes #14030 (#14046)

* base `parseEnum` on a case statement, fixes #14030

* apply simplifactions / clean up, remove `norm` node, use strVal

* export `normalize` in json.nim

* cmp using nimIdentNormalize, error at CT if ambiguous enum found

`nimIdentNormalize` provided by @cooldome.

We track all names of the branches we have created so far and error if
a duplicate is found.

Dummy change to make github react...

* fix docstring of `nimIdentNormalize`

* make `typ` arg `typedesc`, add lineinfo, call norm. only once

tests/stdlib/tstrutil.nim

@@ -348,3 +348,90 @@ when true:
 
 main()
 #OUT ha/home/a1xyz/usr/bin
+
+
+# `parseEnum`, ref issue #14030
+# check enum defined at top level
+type
+  Foo = enum
+    A
+    B = "bb"
+    C = (5, "ccc")
+    D = 15
+    E = "ee" # check that we count enum fields correctly
+
+block:
+  let a = parseEnum[Foo]("A")
+  let b = parseEnum[Foo]("bb")
+  let c = parseEnum[Foo]("ccc")
+  let d = parseEnum[Foo]("D")
+  let e = parseEnum[Foo]("ee")
+  doAssert a == A
+  doAssert b == B
+  doAssert c == C
+  doAssert d == D
+  doAssert e == E
+  try:
+    let f = parseEnum[Foo]("Bar")
+    doAssert false
+  except ValueError:
+    discard
+
+  # finally using default
+  let g = parseEnum[Foo]("Bar", A)
+  doAssert g == A
+
+block:
+  # check enum defined in block
+  type
+    Bar = enum
+      V
+      W = "ww"
+      X = (3, "xx")
+      Y = 10
+      Z = "zz" # check that we count enum fields correctly
+
+  let a = parseEnum[Bar]("V")
+  let b = parseEnum[Bar]("ww")
+  let c = parseEnum[Bar]("xx")
+  let d = parseEnum[Bar]("Y")
+  let e = parseEnum[Bar]("zz")
+  doAssert a == V
+  doAssert b == W
+  doAssert c == X
+  doAssert d == Y
+  doAssert e == Z
+  try:
+    let f = parseEnum[Bar]("Baz")
+    doAssert false
+  except ValueError:
+    discard
+
+  # finally using default
+  let g = parseEnum[Bar]("Baz", V)
+  doAssert g == V
+
+block:
+  # check ambiguous enum fails to parse
+  type
+    Ambig = enum
+      f1 = "A"
+      f2 = "B"
+      f3 = "A"
+
+  doAssert not compiles((let a = parseEnum[Ambig]("A")))
+
+block:
+  # check almost ambiguous enum
+  type
+    AlmostAmbig = enum
+      f1 = "someA"
+      f2 = "someB"
+      f3 = "SomeA"
+
+  let a = parseEnum[AlmostAmbig]("someA")
+  let b = parseEnum[AlmostAmbig]("someB")
+  let c = parseEnum[AlmostAmbig]("SomeA")
+  doAssert a == f1
+  doAssert b == f2
+  doAssert c == f3