Consider making driver dependencies extras

[sk-]

Currently when installing clickhouse-sqlalchemy one gets the following transitive dependencies:

• asynch: for asynch driver
• clickhouse-driver: for native driver
• requests: for http driver

This is understandable to provide a good out of the box experience for all users, however it comes with a baggage of bringing lots of extra dependencies, as one will typically use just one driver.

├── clickhouse-sqlalchemy v0.3.2
│   ├── asynch v0.3.1
│   │   ├── ciso8601 v2.3.3
│   │   ├── leb128 v1.0.9
│   │   ├── lz4 v4.4.5
│   │   ├── pytz v2025.2
│   │   ├── tzlocal v5.3.1
│   │   └── zstd v1.5.7.3
│   ├── clickhouse-driver v0.2.10
│   │   ├── pytz v2025.2
│   │   └── tzlocal v5.3.1
│   ├── requests v2.32.5
│   │   ├── certifi v2026.2.25
│   │   ├── charset-normalizer v3.4.5
│   │   ├── idna v3.11
│   │   └── urllib3 v2.6.3
│   └── sqlalchemy v2.0.48 (*)

It would be ideal if driver dependencies could be controlled by the use of extras.