fix: use a growable bloom filter implementation.

[peterhuene]

This PR replaces the fast bloom filter implementation with a growable one.

A growable implementation is required as the bloom filter is used within a
generator; the number of elements in the bloom filter is unbounded and
dependent upon how many docker tasks are spawned rather than how many docker
tasks may spawn concurrently.

Included with these changes:

• Use thiserror for custom error types (the crate was already a transitive
  dependency).
• Replace Option<NonEmpty<C>> where C is a collection type with the
  collection type itself; this makes the API more ergonomic.
• Replace args in Execution with program and args; this makes the API a
  little less confusing as not everything is put into args. The name
  program was chosen as that's what std::process::Command::new uses.
• Deleted a few unused builder.rs files.
• Remove the UI dependency from Engine and tracking tasks from Runner to
  make it Send+Sync. The UI is moved into relevant main.rs files.

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