Weighted load balancing policy

[akhaku]

This PR open-sources the work Joey Lynch and I did and presented at ApacheCon 2022. It requires a bit of work before it's mergeable, but hoping to get some feedback on a couple areas before I put in much more work. A couple major things left to do:

• Port the tests we added internally. We also have some jmh tests but I'm not sure if those will fit in the driver codebase
• Pass the local rack through to the driver. Internally we passed it through the context, for OSS perhaps the right thing it to implement something like the optional/required local DC pattern.
• The documentation could probably use some more work, but I'd love guidance on where to focus that: the implementation class? Or reference.conf?

[akhaku]

Additionally, this will tackle JAVA-3040

[aratno]

The documentation could probably use some more work, but I'd love guidance on where to focus that: the implementation class? Or reference.conf?

I'd put configuration documentation in reference.conf. For more context on why someone would benefit from this LBP over the default, put that in manual/core/load_balancing/README.md.