Proposal: add TestBaseVCI support to python-can

Hi maintainers,

We are a company that develops CAN bus communication and simulation products, and I'd like to ask whether support for our TestBaseVCI CAN / CAN FD hardware could be accepted in python-can.

We already have a working backend for it, and it has been used for quite a while as a separately distributed extension. The current backend name is `hrcan`, with bus class `HRCANBus`.

Current status:
- supports classic CAN and CAN FD
- has been used in practice for a long time
- currently installed manually by copying files into the Python environment and registering it in `can.interfaces.BACKENDS`

Environment:
- Windows 10 / 11
- Ubuntu 20 / 22
- 64-bit Python
- TestBaseVCI driver >= 2.4.1
- currently used with python-can 4.5.0

Supported features:
- start CAN / CAN FD channels with different bus parameters
- send / receive single frames
- periodic transmission, with manual and logger-based receive flows
- multi-device support
- multi-process support
- unified timestamp behavior

A few notes before I prepare a PR:
- I will only submit the Python-layer adapter code to python-can
- if a user wants to use our hardware but has not installed the SDK / device driver, I can provide a public SDK download link and a clear text reminder
- I will make sure that if users do not use our device, this support will not affect any existing python-can functionality

If this direction looks okay, I'm happy to clean it up and prepare a PR. I'd also appreciate any suggestions before I start.

Thanks.