Rollup merge of #52033 - zachrwolfe:outdated_value_comment, r=oli-obk
Rollup merge of #52033 - zachrwolfe:outdated_value_comment, r=oli-obk

[Gardening] Update outdated comments: ByVal -> Scalar

ByVal enum cases in mir::interpret::value were renamed to Scalar a while ago but comments still refer to the old names.

GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,graydon/rust,aidancully/rust