Use size_t instead of int to represent object size in CDS code

Parts of the CDS code uses int to represent the size of an object. These should be change to size_t.

Example:

http://hg.openjdk.java.net/jdk/jdk/file/1512d88b24c6/src/hotspot/share/classfile/compactHashtable.cpp#l73

size_t CompactHashtableWriter::estimate_size(int num_entries) {
  int num_buckets = calculate_num_buckets(num_entries);
  size_t bucket_bytes = MetaspaceShared::ro_array_bytesize<u4>(num_buckets + 1);

  // In worst case, we have no VALUE_ONLY_BUCKET_TYPE, so each entry takes 2 slots
  int entries_space = 2 * num_entries;
  size_t entry_bytes = MetaspaceShared::ro_array_bytesize<u4>(entries_space);

  return bucket_bytes
       + entry_bytes
       + SimpleCompactHashtable::calculate_header_size();
}

We should also add asserts to prevent integer overflow in the final addition expression.