Can we drop D9 support from the 4.x branch?

Problem/Motivation

Currently the need to support D9 prevents us from using newer features such as object oriented hooks. It also requires us to stay PHP 7.4 compatible, which precludes us from using D8 features such as attributes.

Before making this change, I would like to confirm that there is no compelling case for keeping 9.x support. If you are still using Drupal 9, please comment below.

I believe dropping support for unsupported versions of Drupal does not require a change of major version.

Steps to reproduce

N/A

Proposed resolution

• Wait for confirmation that D9 support can be dropped.
• Drop ^9.5 from core_version_requirement in .info.yml file.
• Increase PHP requirement in composer.json from `">=7.4"` to `">=8.1"`.

Remaining tasks

Currently waiting for any objections to removing support for D9.

User interface changes

N/A

API changes

N/A

Data model changes

N/A