feat(relayer): add indexer in MySQL

[xiaodino]

In https://github.com/taikoxyz/taiko-mono/blob/main/packages/relayer/pkg/repo/block.go#L49

func (r *BlockRepository) GetLatestBlockProcessedForEvent(eventName string, chainID *big.Int) (*relayer.Block, error) {
	b := &relayer.Block{}
	if err := r.
		startQuery().
		Raw(`SELECT id, block_height, hash, event_name, chain_id 
		FROM processed_blocks 
		WHERE block_height = 
		( SELECT MAX(block_height) from processed_blocks 
		WHERE chain_id = ? AND event_name = ? )`, chainID.Int64(), eventName).
		FirstOrInit(b).Error; err != nil {
		return nil, err
	}

	return b, nil
}

The database query scans rows in processed_blocks and it's being used heavily based on the database monitoring.

Other query is

SELECT * FROM `processed_blocks` WHERE `block_height` = ? AND `chain_id` = ? ORDER BY `processed_blocks` . `id` LIMIT ?

The PR is to add indexer to optimize the database performance.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5a1f671) 26.82% compared to head (f2ed0f6) 26.82%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #15927   +/-   ##
=======================================
  Coverage   26.82%   26.82%           
=======================================
  Files         105      105           
  Lines        6188     6188           
=======================================
  Hits         1660     1660           
  Misses       4348     4348           
  Partials      180      180           

Flag	Coverage Δ		*Carryforward flag
eventindexer	17.22% <ø> (ø)		Carriedforward from 5a1f671
guardian-prover-health-check	34.81% <ø> (ø)		Carriedforward from 5a1f671
relayer	37.88% <ø> (ø)

*This pull request uses carry forward flags. Click here to find out more.

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