fix(l2): regenerate head state in node initialization

[ilitteri]

Motivation

Since the path-based feature was added, the database stores the state 128 blocks behind the head block, while the state of the blocks in between is kept in in-memory-diff-layers.

After the node is shut down, those in-memory layers are lost, and the database won't have the state for those blocks. It will have the blocks, though.

When the node is started again, the state needs to be regenerated by re-applying the blocks from the last known state root up to the head block.

This is already handled in the L1 node, but not in the L2 node.

Description

Calls regenerate_head_state during L2 node initialization.

[Copilot]

Pull Request Overview

This PR adds state regeneration functionality to L2 node initialization to handle the loss of in-memory diff layers after node restarts. Since the path-based feature stores state 128 blocks behind the head block with intermediate states in memory, these need to be regenerated on startup.

Key Changes:

• Calls regenerate_head_state during L2 node initialization (matching existing L1 behavior)
• Makes regenerate_head_state public and adds comprehensive documentation
• Improves code formatting and comments in the regeneration logic

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
cmd/ethrex/l2/initializers.rs	Imports and calls regenerate_head_state after blockchain initialization
cmd/ethrex/initializers.rs	Makes regenerate_head_state public, adds documentation, and improves code formatting

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[github-actions]

Lines of code report

Total lines added: 9
Total lines removed: 0
Total lines changed: 9

Detailed view

+--------------------------------------+-------+------+
| File                                 | Lines | Diff |
+--------------------------------------+-------+------+
| ethrex/cmd/ethrex/initializers.rs    | 466   | +8   |
+--------------------------------------+-------+------+
| ethrex/cmd/ethrex/l2/initializers.rs | 250   | +1   |
+--------------------------------------+-------+------+