Determine performance impact of using (init|clean|clear_up) list source functions

[Long-lived invariant violation issue](https://github.com/diffblue/cbmc/issues/5344) has been fixed so it may be possible to avoid stubbing out these functions `aws_cryptosdk_*_(init|clean|clear_up)` functions.

Many proofs in this repository include stubs for these functions so the next step would be to study how not including them would affect their performance. If the performance is good, we can avoid using these stubs altogether.

Start by locating the repository proofs that stub aws_cryptosdk_*_(init|clean|clear_up), then compare their performance with those stubs removed. Review the linked long-lived invariant violation issue for context; done means determining whether the performance impact supports removing the stubs altogether.

Written by the indexing model from the issue text.