chore: engine integration tests refactoring

[aleksuss]

Description

The main goal of the PR is to replace the deprecated near-sdk-sim crate with the aurora-engine-workspace crate, which is based on workspaces. Also, some test files have been restructured.

Performance / NEAR gas cost considerations

No changes in gas costs.

[joshuajbouw]

Let me know when this is rebased, I'll be pulling it in and including for the release.

[aleksuss]

@joshuajbouw Done.