Introduce configuration with distro

[lzchen]

In order to encapsulate custom azure components and configuration, the distro will now allow users the ability to instantiate everything that is needed for an opentelemetry workflow to azure monitor, with the ability to configure the components using params. This will be done using a new distro api configure_opentelemetry as shown below:

from opentelemetry import trace
from azure.monitor.opentelemetry.distro import configure_opentelemetry

configure_opentelemetry()

tracer = trace.get_tracer(__name__)

with tracer.start_as_current_span("hello2"):
    print("Hello, World!")

input()

Things to note:

1. This PR adds only the barebones skeleton, and only allows manual configuration of some variables (service.name and such)
2. Autoinstrumentation capabilities remain unchanged. Autoinstrumentation workflow will be refactored to use common code in the added distro api but will remain a TODO.
3. Everything in this PR is a proposal and subject to discussion/change. The idea is to create a bunch of working customer scenarios that will show the value of the distro api.