RFR: 8260630: Templatize literal_size

[Kim Barrett]

Please review a couple of small cleanups in Hashtable support.

(1) Replace some "default" overloads for literal_size with a template.  This
makes it easier to add new Hashtable value types whose sizes aren't
interesting for statistics printout.

(2) Trivial change to remove no longer used instantiation of Hashtable
support for oop values.

Testing:
mach5 tier1

-------------

Commit messages:
 - remove instantiations for oop
 - templatize literal_size

Changes: https://git.openjdk.java.net/jdk/pull/2310/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2310&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8260630
  Stats: 14 lines in 1 file changed: 1 ins; 11 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2310.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2310/head:pull/2310

PR: https://git.openjdk.java.net/jdk/pull/2310