EVM: failsafe storage in /tmp/evm and not just /tmp

Context

The current behavior of the failsafe storage is:

1. Copy /evm to /tmp
2. Every code that writes or reads to the storage just takes the key-path, e.g. /ticketer and the failsafe storage adds the prefix /tmp, therefore it becomes /tmp/ticketer.
3. At the end, it we promote the storage we move /tmp/ticketer to /evm/ticketer.

This was actually a very bad idea, it's not clear whether you need to add the /evm prefix or not, because some hidden code does it for you. We've made the mistake multiple times. As we'll move the failsafe storage to /evm/world_state only, I cannot live anymore with the automatic /evm prefix, it just wouldn't work, I can explain this in details if required. Therefore I again a preliminary step, by redefining the current failsafe storage without modifying overall its behavior.

This merge requests must not change any path. It should purely modify the internal state of the kernel in the kernel_entry.

Manually testing the MR

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