feat(cli): make stopping on invalid block the default for reth import

[mattsse]

Summary

When importing blocks, the import now stops at the last valid block by default if an invalid block is encountered during execution or validation. The database is left at the last valid block state.

A new --fail-on-invalid-block flag is provided to restore the original behavior of failing entirely when an invalid block is encountered.

Motivation

This is the expected behavior for Hive consensus tests that import chains with intentionally invalid blocks. From the Hive consensus test documentation:

The client should start even if the blocks are invalid, i.e. after the import, the client's 'best block' should be the last valid, imported block.

Previously, reth failed entirely when encountering invalid blocks during import, causing these Hive tests to fail. Now this behavior is the default, and the old behavior can be restored with --fail-on-invalid-block.

Implementation

• Modified ImportConfig to use fail_on_invalid_block field (default: false)
• Extended ImportResult with stopped_on_invalid_block, bad_block, and last_valid_block fields
• Added is_successful() method to ImportResult
• Use Pipeline::run_loop() by default to handle ControlFlow::Unwind gracefully
• Use Pipeline::run() when --fail-on-invalid-block is set
• Updated CLI documentation and book via make update-book-cli

Usage

Default behavior (stop at last valid block):

reth import chain.rlp

Old behavior (fail on invalid block):

reth import --fail-on-invalid-block chain.rlp

Testing

• All unit tests pass (40/40)
• Clippy passes with no warnings
• Code is properly formatted
• Hive consensus tests pass: Tested with bcInvalidHeaderTest suite (22/22 tests passing including wrongStateRoot, wrongGasUsed, wrongParentHash, etc.)