objectcache: Use variadic signature for makeKey()

objectcache: Use variadic signature for makeKey()

This should help fix the following issues that various repos
are getting from Phan as of late:

> Call with 5 arg(s) to \BagOStuff::makeKey() which only takes 2 arg(s)
> defined at ../../includes/libs/objectcache/BagOStuff.php:456
> <source="PhanParamTooMany"/>

Bug: T228563
Depends-On: I5cfba063821101325a5a7359e6b8ad71a0fb1b2f
Depends-On: Ifa5b96735376f2fbe3680799f960616ba8d357ff
Change-Id: Ic9df7f3ad7f356c7cbdfe1edfbe35821b931dda6