Java SDK: Rename annotation namespace from Builder to Airflow

[jason810496]

Why

@Airflow.* makes it clear that they declare Airflow Dags and tasks.

What

• Rename the annotation container org.apache.airflow.sdk.Builder to org.apache.airflow.sdk.Airflow.

// Before
@Builder.Dag(id = "my_pipeline", schedule = "@daily")
public class MyPipeline {
  @Builder.Task(id = "extract", retries = 2)
  public long extract(Client client) { ... }

  @Builder.Deps
  static class Wiring implements MyPipelineDeps { ... }
}

// After
@Airflow.Dag(id = "my_pipeline", schedule = "@daily")
public class MyPipeline {
  @Airflow.Task(id = "extract", retries = 2)
  public long extract(Client client) { ... }

  @Airflow.Deps
  static class Wiring implements MyPipelineDeps { ... }
}

• The same rename applies to @Airflow.If, @Airflow.Switch, @Airflow.TaskGroup and @Airflow.TaskHandler.
• The generated <Class>Builder class and its build() method do not change.
• Rename BuilderProcessor to AirflowProcessor, and its test to match.
• Update the user docs, README, module docs, examples, e2e and k8s test bundles. ADRs are left as historical records.

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[github-actions]

Backport successfully created: v3-4-test

Note: As of Merging PRs targeted for Airflow 3.X
the committer who merges the PR is responsible for backporting the PRs that are bug fixes (generally speaking) to the maintenance branches.

In matter of doubt please ask in #release-management Slack channel.

Status	Branch	Result
✅	v3-4-test