[10.x] Fixed method and passthru in Eloquent builder both to lowercase

[bertoost]

Prevents users using the passthru list running into breaking changes and not being aware of the casing change. See PR 48852 - #48852 (comment)

[taylorotwell]

Not sure we to add the performance hit of an extra array_map.

[bertoost]

Cool @taylorotwell
You have introduced a change somewere on the road between 10.29 and 10.30 where our own Builder failed and we searched for the issue for a couple of hours...
I suggest an extra change to avoid this problem for anyone else in the future...
You at least could have a small talk about the approach instead of closing it without...
Too bad.