Proof that #6324 is not a bug.

[esdrubal]

Description

The reproduction presented in #6324 was missing loading the storage configuration properly.

To do that we have to use the following in test/src/sdk-harness/test_projects/run_external_proxy_with_storage/mod.rs:

StorageConfiguration::default().add_slot_overrides_from_file("test_projects/run_external_target_with_storage/out/release/run_external_target_with_storage-storage_slots.json").unwrap();

This commit changes the presented reproduction to load the storage slots and the test runs without reverting.

Closes #6324

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
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• I have added tests that prove my fix is effective or that my feature works.
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