cli: scaffold bisect noun with start and run verbs

Introduce initial structure for the `bisect` noun with `start` and `run`
verbs in the FastPath CLI. These will support automated kernel regression
bisection workflows.

- Adds CLI argument parsing for `fastpath bisect start`
- Adds CLI argument parsing for `fastpath bisect run`
- Registers both verbs under a new `bisect` noun
- Includes placeholder dispatch() methods for future logic

This sets up the interface and CLI plumbing in preparation for the
bisection plan generation and benchmark evaluation implementation.

Signed-off-by: Aishwarya TCV <aishwarya.tcv@arm.com>