Add --accountkey as a valid flag for account switching

[securitylevelup]

The cli-appsec allows for account switching and currently only accepts --account_key. Other Akamai CLI packages are using --accountkey which is causing confusion.

Could you please add --accountkey as a valid flag and make sure that both --accountkey / --account_key work to switch your account?

--account-key works.
--accountkey does not work.

Please also update the documentation and built-in help command to reflect that both flags can be used.

Thanks in advance.