create a version of requests that retries on certain HTTP statuses by default

[rudolfix]

Motivation

1. Most of the pipelines do hundreds of requests, if there's no retry built in the whole pipeline will fail.
2. We want a blueprint for "source helper" - something that is so often used that is a part of dlt core

Tasks

1. implement retry session using HTTPAdapter: https://majornetwork.net/2022/04/handling-retries-in-python-requests/
2. allow to configure timeout as well.
3. provide a default session with sane timeout and retry parameters
4. provide configurable session like: https://github.com/bustawin/retry-requests
5. look at thread safety ie. here someone explains how to make a shared connection pool which is thread safe https://stackoverflow.com/questions/18188044/is-the-session-object-from-pythons-requests-library-thread-safe

Place code in dlt.sources.helpers.requests module and expose the default session as requests and configurable session as requests_with_retry(...)

the point of the above is to provide drop-in replacement for people making requests in pipelines repository, They'd just import from some other module but the remaining code could stay the same.