feat: introduce init_tip_hash setting for indexer to skip previous block synchronization

[EthanYuan]

What problem does this PR solve?

Problem Summary:

CKB-indexer supports building indexes only for interested blocks. This can be done by setting block_filter before this PR. But the filter can only traverse the block from 0 and for the uninterested block also need to save its Header(BlockNumber, &'a Byte32, bool).

What is changed and how it works?

This pr introduces the init_tip_hash setting. The init tip is effective as long as it is set higher than the current height of the indexing head (reboot required), as the starting height of the indexing. This provides the following benefits:

1. synchronization can be started instantly from any height block (by block hash)
2. the previous block does not need to save any data

What's Changed:

• Added commented out configuration item to ckb.toml template (as an example)
• Implement apply_init_tip function, which is called in IndexerService::spawn_poll
• The reset-data --indexer option is supported.

Related changes

This feature will also be used for index-r:

• feat: add rich-indexer which is another built-in indexer based on relational database #4224

Check List

Tests

• Manual test
  • general: the indexer can skip the synchronization of the block before the init tip, and the init tip block only saves the block Header(BlockNumber, &'a Byte32, bool)
  • the init tip is effective as long as it is set higher than the current height of the indexing head (reboot required)
  • when the header corresponding to the init_tip_hash is not found, it will attempt to continue searching, and the indexing service of the indexer will not start

Release note

Title Only: Include only the PR title in the release note.