Change target-bigquery default variant to one of the SDK based ones

[DouweM]

I think we should make https://hub.meltano.com/loaders/target-bigquery--youcruit/ (showcased in https://meltano.com/blog/6x-more-speed-for-your-data-pipelines-with-batch-messages/) or https://hub.meltano.com/loaders/target-bigquery--z3z1ma/ (By Alex @ Harness) the default target-bigquery variant as it’s built with the SDK and supports BATCH.

[pnadolny13]

This is a good idea especially because we've seen a fair amount of users hit hard failures in the adswerve variant due to data types and it doesnt look like theyre prioritizing supporting a fail safe type adswerve/target-bigquery#35.

I'm not sure how we decide which variant becomes default out of the 2 SDK based versions. It seems like Alex has tried to build a more feature rich/optimized version so from a surface level exploration I'd probably vote for that one but clearly the youcruit version is good as well based on the blog post. I wonder if we should ask them directly if either want to consolidate effort on one of the variants, or volunteer to not be default. We could also ask the community to weigh in on this if they have experience with either.

[tayloramurphy]

I'm generally supportive - hard to say if there are any critical missing features from an SDK-based one. But if folks are feeling confident we can make the switch.