Integrate `impit` as HTTP client

[vdusek]

• Impit is already available on PyPI: impit.
• Integrate it as the HTTP client, and make it a default one, while keeping HTTPX optional.
• Breaking change?
• The apify_fingerprint_datapoints, browserforge and httpx[brotli,http2,zstd] could be then removed from the mandatory dependencies.
• Relates to: Optimize package footprint by removing unnecessary deps #1077.