gh-112064: Fix incorrect handling of negative read sizes in `HTTPResponse.read()...

gh-112064: Fix incorrect handling of negative read sizes in `HTTPResponse.read()` (#128270)

The parameter `amt` of `HTTPResponse.read()`, which could be a negative integer,
has not been handled before and led to waiting for the connection to close
for `keep-alive connections`. Now, this has been fixed, and passing negative values
to `HTTPResponse().read()` works the same as passing `None` value.