Add pre_state_root in evm hook

[bkolad]

Description

This PR introduces the following changes:

1. Adds handling for the pre_state_root in begin_slot_hook.
2. Refactors evm tests.

Fix #876

Testing

Ci passes.

Docs

No doch changes.

[codecov]

Codecov Report

Merging #986 (99639f3) into nightly (20c001a) will decrease coverage by 0.1%.
The diff coverage is 87.5%.

Files	Coverage Δ
...system/module-implementations/sov-evm/src/hooks.rs	96.1% <100.0%> (+0.1%)	⬆️
...em/module-implementations/sov-evm/src/evm/tests.rs	97.3% <71.4%> (-0.2%)	⬇️

... and 2 files with indirect coverage changes

[orkunkilic]

LGTM!