Remove redundant startup logs from `crewai run` and make the legacy flow
command warning actionable.
- Stop printing `Running the Flow` and `Running the Crew` before project
execution.
- Stop printing the redundant `Flow started with ID: ...` line while
preserving flow lifecycle event emission.
- Replace Click's generic `kickoff` deprecation warning with a clearer
message that tells users to use `crewai run`.
* Add declarative Flow CLI support
Currently, declarative flows can be loaded by the runtime, but the CLI
still treats them as an experimental definition file instead of a
first-class Flow project shape.
With this PR, `crewai create flow --declarative` scaffolds a YAML-backed
Flow project, and `crewai run`, `crewai flow kickoff`, and `crewai flow
plot` can run against the configured definition.
This also lets crew actions reference reusable crew definition files or
folders and override their inputs from the Flow definition, so
declarative flows can compose existing declarative crews without
inlining everything.
* Address code review comments
