[DEPENDENCY_REFACTOR] - Move all the dependency code into consensus2

[shenkeyao]

Closes #3292.

This PR:

• Reorganizes functions in the helpers.rs and view_changes.rs files for the consensus task:
  • Moves non-dependency-task functions to task-impls/src/consensus/handlers.rs.
  • Moves functions shared by dependency and non-dependency tasks to task-impls/src/helpers.rs.
• Gates dependency- and non-dependency-task implementations in hotshot/src/tasks/task_state.rs.
• Removes redundant feature gates and updates imports.

This PR does not:

• Change any implementation logic.

Key places to review:

• Files with pure addition or deletion could be skipped for review, since the changes are mainly function movings that git doesn't recognize.

[bfish713]

Looks good, I will re-aprove after that's resolved, and CI should be green after merging main