### Description

1st part of #1369, mainly on pi circuit integration


### Issue Link

#1369 

### Type of change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] This change requires a documentation update

### Contents

- `Withdrawal` struct definition and `WdTable` implementation
- adding `withdrawals` and `withdrawal_root` in block struct
- `wd_table` assignment in pi circuit

…-4896 withdrawals==None (#1688)

### Description

Integration Tests have been failing since introduction of
#1369,
due to Option::Unwrap on None value, when eth_block.withdrawals==None.

### Type of change

- [x] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] This change requires a documentation update

### Contents

- zkevm-circuits/zkevm-circuits/src/witness/block.rs

### Rationale
replace eth_block.withdrawals.clone().unwrap() with
eth_block.withdrawals.clone().unwrap_or_default()

### How Has This Been Tested?

https://github.com/privacy-scaling-explorations/zkevm-circuits/actions/runs/6968928576/job/18963801769
<hr>

### Issue

#1687