Convert Python timestamps to UUID without float multiplication

Description

After investigating https://datastax-oss.atlassian.net/browse/PYTHON-898. This multiplication may produce unexpected results
for example if

Then that multiplication would produce

I think this is not an issue because uuid_from_time is used to generate unique UUIDs from timestamps and that's still happening.

Environment

None

Pull Requests

None

Assignee

Jim Witschey

Reporter

Jaume Marhuenda