stdlib: Sprinkle an __always inline onto Range.index(after:)
stdlib: Sprinkle an __always inline onto Range.index(after:)

After moving to the new llvm pass pipeline this function no longer gets
inlined. Leading to 150% regressions in ObjectiveCBridge benchmarks.

rdar://98533158

roambotics/swift,roambotics/swift,glessard/swift,apple/swift,benlangmuir/swift,glessard/swift,glessard/swift,benlangmuir/swift,glessard/swift,apple/swift,roambotics/swift,glessard/swift,benlangmuir/swift,benlangmuir/swift,roambotics/swift,benlangmuir/swift,glessard/swift,apple/swift,apple/swift,roambotics/swift,apple/swift,roambotics/swift,apple/swift,benlangmuir/swift