Auto merge of #139849 - thaliaarchi:args/zkvm, r=ibraheemdev

Fix `env::ArgsOs` for zkVM

The zkVM implementation of `env::ArgsOs` incorrectly reports the full length even after having iterated. Instead, use a range approach which works out to be simpler. Also, implement more iterator methods like the other platforms in #139847.

cc `@flaub` `@jbruestle` `@SchmErik`

Author: bors