counts specified in runtime.h.

In the vast majority of the cases when we call into the runtime we use
the default number of arguments. Hence, there is not need to specify it
again. This CL also removes TailCallExternalReference as there were no
users.

BUG=

Review URL: https://codereview.chromium.org/1553703002

Cr-Commit-Position: refs/heads/master@{#33066}