Feat: Fix examples, rework Context classes

[mrkaye97]

Couple things here:

1. Merged in the new workflows + Pydantic settings changes, which means we can get rid of load_dotenv everywhere 🥳
2. Using the new workflow approach in all of the examples, including subclassing the BaseWorkflow, constructing config, and, when necessary, creating some input_validator classes (e.g. in the fanout examples)
3. Reworked the context to be a single class - there was way too much abstraction there for what it was IMO
4. Ripped out the V1 Hatchet class + WorkflowMeta and associated code

[mrkaye97]

FYI @grutt - this should be a fix to hard-coding that token env var (the thing we talked about a week or two ago - this)

[mrkaye97]

merged this optimistically too - can circle back to any comments!