perf(database): add reserve calls in merge_transitions and extend_state

[gakonst]

Summary

Pre-allocate hashmap capacity before inserting in loops to reduce rehashing overhead.

Changes

• apply_transitions_and_create_reverts: reserve self.state for incoming transitions
• update_and_create_revert / extend_storage: reserve this_storage for storage_update
• extend_state: reserve self.state for other_state, and this.storage for per-account storage

Prompted by: DaniPopes

[codspeed-hq]

Merging this PR will not alter performance

✅ 176 untouched benchmarks

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_{Comparing danipopes/reserve-in-merge-transitions (de202c2) with main (3bccc97)}