processPendingDeposits can jump as high as 1.2s on epoch transitions

### Describe the bug

~~Since fulu~~, processPendingDeposits can take up to 1.2s during epoch transitions more frequently and at a higher cost in processing time than Electra.

### Expected behavior

We need to minimize overhead cost and frequency of these spikes to at least Electra levels or better.

### Steps to reproduce

_No response_

### Additional context

_No response_

### Operating system

Linux

### Lodestar version or commit hash

v1.35.0-rc.1