rename CompositeHTTPPropagator, add deprecation notice

[codeboten]

Description

Renaming CompositeHTTPPropagator to CompositePropagator. Note this change adds the dependency on the Deprecated package to the API, we may or may not want this, would love some feedback from reviewers. The following is what users will see when using CompositeHTTPPropagator:

>>> from opentelemetry.propagators.composite import CompositeHTTPPropagator
>>> CompositeHTTPPropagator([])
<stdin>:1: DeprecationWarning: Call to deprecated class CompositeHTTPPropagator. (You should use CompositePropagator) -- Deprecated since version 1.2.0.
<opentelemetry.propagators.composite.CompositeHTTPPropagator object at 0x108712be0>

Fixes #1775

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

Does This PR Require a Contrib Repo Change?

• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been updated

[ocelotl]

We should leave the documentation as it is for deprecated objects, besides that, LGTM 👍

[codeboten]

@ocelotl PTAL

[ocelotl]

@ocelotl PTAL

Approved 👍