chore: admin fund amount

[lesterli]

Summary

This PR updates to fund the admin address with 0.1ether and also:

• replaced command readarray with a more portable way to create an array from the prefunded accounts that works on both macOS and Linux
• .gitignore for .env.bak*, b/c running make l2-gen-addresses could generate the backup file env.bak-xxx if addresses already exist

Test Plan

launch local l1:

make l1-configure
make l1-launch
make l1-verify

update the .env:

L1_RPC_URL=http://localhost:18545
L1_BEACON_URL=http://localhost:15052
L1_CHAIN_ID=11155222
L1_FUNDED_PRIVATE_KEY=<the key's value in the configs/l1/l1-prefund-wallet.json>

test it and the output:

make l2-gen-addresses

Generated new addresses and updated .env file.
Funding ADMIN address: 0x5B46F34d400704EbcD408282c848d8c6e523EE88 with amount 0.1ether
...
Funding BATCHER address: 0xf2125cD1Bf90EC81EC0FEFc434d8C38AB4Fa5A39 with amount 1ether
...
Funding PROPOSER address: 0x22Cc0752894A7B7F9A8dAb1E94ac5d170aE84667 with amount 1ether


Funding complete.

use cast to verify, it should also return 0.1

cast balance <admin address in the .env> -e --rpc-url http://localhost:18545