New: support engagement against a specified quantum processor endpoint

[kalzoo]

Description

This PR adds an endpoint_id argument to both QPU and get_qc, as well as support for engagement-to-endpoint within EngagementManager.

Checklist

• The PR targets the rc branch (not master).
• Commit messages are prefixed with one of the prefixes outlined in the commit syntax checker (see pattern field).
• The above description motivates these changes.
• There is a unit test that covers these changes.
• All new and existing tests pass locally and on the PR's checks.
• Parameters and return values have type hints with PEP 484 syntax.
• Functions and classes have useful Sphinx-style docstrings.
• All code follows Black style and obeys flake8 conventions.
• (New Feature) The docs have been updated accordingly.
• (Bugfix) The associated issue is referenced above using auto-close keywords.
• The changelog is updated, including author and PR number (@username, Test ignore #1234).

[ameyer-rigetti]

Implementation looks good, just had some test-related comments.

[dbanty]

Looks good, most of these are just nitpicks, I'll approve once the commented-out debug statement is cleared.

[dbanty]

Looks great! 🚀

[rigetti-githubbot]

🎉 This PR is included in version 3.0.1-rc.2 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀

[rigetti-githubbot]

🎉 This PR is included in version 3.0.1 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀