[Feat][V2] Implement simple plugin in executor

[popojk]

Tracking issue

Related to #6705

Why are the changes needed?

Implement a simple plugin to v2 Executor. The plugin will just transit to next plugin phase, not implementing business logic yet.

How was this patch tested?

Run the test script by executing make run-testclient in manager dir, the output shows that the plugin phase will transit as expected

Labels

Please add one or more of the following labels to categorize your PR:

• added: For new features.

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

[flyte-bot]

Bito Automatic Review Skipped - Draft PR

Bito didn't auto-review because this pull request is in draft status.
No action is needed if you didn't intend for the agent to review it. Otherwise, to manually trigger a review, type /review in a comment and save.
You can change draft PR review settings here, or contact your Bito workspace admin at eduardo@union.ai.

[flyte-bot]

Bito Automatic Review Skipped - Branch Excluded

Bito didn't auto-review because the source or target branch is excluded from automatic reviews.
No action is needed if you didn't intend for the agent to review it. Otherwise, to manually trigger a review, type /review in a comment and save.
You can change the branch exclusion settings here, or contact your Bito workspace admin at eduardo@union.ai.