The first operand to the CallRuntime class of bytecodes is the
ID of the runtime function being called. Before this commit
the ID was printed as plain uint16_t, now we get something like:

  B(CallRuntime) U16(Runtime::Add) ...

This change is intended to make both the golden files more
resistant to modifications of the i::Runtime::FunctionId enum
and the output of generate-bytecode-expectations more readable.

BUG=v8:4280
LOG=N

Review URL: https://codereview.chromium.org/1723223002

Cr-Commit-Position: refs/heads/master@{#34224}