Implement Skylark function repr

Move printing code from EvalUtils to Printer.
Rename functions in Printer:
printValue becomes str or print,
prettyPrintValue becomes repr or write,
formatString becomes format,
makeFormattable becomes strFormattable,
prettyPrintValues becomes listString.

write being self-sufficient is made the reference,
and print is the one that is a wrapper around write,
rather than the other way around, avoiding mutual recursion.

--
MOS_MIGRATED_REVID=95897834
diff --git a/src/test/java/com/google/devtools/build/lib/syntax/SkylarkShell.java b/src/test/java/com/google/devtools/build/lib/syntax/SkylarkShell.java
index f00d8f5..c4bb7d8 100644
--- a/src/test/java/com/google/devtools/build/lib/syntax/SkylarkShell.java
+++ b/src/test/java/com/google/devtools/build/lib/syntax/SkylarkShell.java
@@ -72,7 +72,7 @@
       try {
         Object result = ev.eval(input);
         if (result != null) {
-          System.out.println(EvalUtils.prettyPrintValue(result));
+          System.out.println(Printer.repr(result));
         }
       } catch (Exception e) {
         e.printStackTrace();