Prefer "val !=/== ref" over "val (not) in [ref]" in conditions

This change increases readibility with the following replacements in
conditions:

 * val in [ref] ==> val == ref
 * val not in [ref] ==> val != ref

Change-Id: I52a77aff60c8e46fa5f6290e3a565f58425d9a68
Merge "Prefer "val !=/== ref" over "val (not) in [ref]" in conditions"