Previously, the parameter count for CSA-generated array builtins needed to be
specified both in the TFJ list of builtins as well as in the bootstrapper when
installing each builtin. This patch adds a utility function that returns the
arity of builtins, including CSA-generated array builtins, given the builtin's
name. This function is now used by the bootstrapper and thus removes the need
for the explicit duplication.

R=ishell@chromium.org
BUG=v8:1956
LOG=N

Review-Url: https://codereview.chromium.org/2852833002
Cr-Commit-Position: refs/heads/master@{#45033}