Activity support

[cretz]

What was changed:

Added full activity support including:

• Worker with ability to run multiple concurrently
• Thread-pool-based and fiber-based activities
  • Fibers only supported on Ruby 3.3+ right now due to bug: Investigate issue with Ruby 3.1/3.2 and worker fibers #162
• Class, instance, and definition-based activities
• Ability to customize activity name, executor, and whether it raises on cancel
• Cancellation token like concept with Temporalio::Cancellation
• Full-featured context with cancellation, heartbeating, info, logging, etc
• Worker interceptors
• Sigs and tests for all

Want to help review?

Great! We welcome all reviews/feedback from everyone. If the PR gets too many comments on it, we may create a new PR for another round of comments. I know the 100-file-count can seem daunting, but a lot of it is generated or unimportant code.

What type of reviewer do you want to be?

I want to review high-level design only

Review README.md.

I want to review how the activities work, but do not care about the implementation

In addition to README.md, also review temporalio/test/worker_activity_test.rb.

I want to review the Ruby implementation but do not want to dig into the Rust side

Review everything but what's in temporalio/ext

I want to help review the Rust side including

Review everything. Maybe even go one further and help us solve/understand #162 and why Ruby 3.1/3.2 wakes up queue-pop
fibers on some queue pushes but not others (and if there's a better way for us to wake up a fiber from another thread).

[cretz]

This is basically just a file move from temporalio/lib/temporalio/client/implementation.rb. Only the async activity stuff at the bottom is new.