Implement named parameters in mapping types

[pcaversaccio]

🧐 Motivation

Solidity version 0.8.18 introduced the possibility to use named parameters in mapping types. Since the minimum pragma version was bumped to Solidity version 0.8.19 via #4288, I think it would make sense to implement this new feature to increase the overall code readability.

📝 Details

OZ contracts make extensive use of mappings, and this could be definitely a benefit:

mapping(address owner => mapping(address spender => uint256 amount)) private _allowances;