chore(weave): Add entity/project init style similar to wandb

[andrewtruong]

https://wandb.atlassian.net/browse/WB-27237

Supports passing an explicit entity and project

[codecov-commenter]

Codecov Report

:x: Patch coverage is 39.13043% with 14 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
weave/trace/api.py	39.13%	14 Missing :warning:

:loudspeaker: Thoughts on this report? Let us know!

[circle-job-mirror[bot]]

Preview this PR with FeatureBee: https://beta.wandb.ai/?betaVersion=bf49d35a164a93f876253c1e755fc65b656459be

[neutralino1]

@andrewtruong do we want to merge or close this?