Add notebooks to demonstrate evaluate API capabilities.

[nick863]

Description

In this PR we are adding four notebooks, demonstrating four different types of executables, consumed by evaluate API.

• DAG Flows
• Flex flows
• Prompty
• Standard evaluators See work item 3151837.

All Promptflow Contribution checklist:

• [x] The pull request does not introduce [breaking changes].
• [x] CHANGELOG is updated for new features, bug fixes or other significant changes.
• [x] I have read the contribution guidelines.
• [x] Create an issue and link to the pull request to get dedicated review from promptflow team. Learn more: suggested workflow.

General Guidelines and Best Practices

• [x] Title of the pull request is clear and informative.
• [x] There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

Testing Guidelines

• [x] Pull request includes test coverage for the included changes.

[github-actions[bot]]

promptflow-evals test result

 12 files  ±0   12 suites  ±0   1h 16m 10s :stopwatch: - 43m 16s  15 tests ±0   15 :white_check_mark: ±0  0 :zzz: ±0  0 :x: ±0  180 runs  ±0  180 :white_check_mark: ±0  0 :zzz: ±0  0 :x: ±0 

Results for commit 2e86ef3c. ± Comparison against base commit 35ed6c50.

:recycle: This comment has been updated with latest results.

[github-actions[bot]]

Hi, thank you for your interest in helping to improve the prompt flow experience and for your contribution. We've noticed that there hasn't been recent engagement on this pull request. If this is still an active work stream, please let us know by pushing some changes or leaving a comment.

[github-actions[bot]]

Hi, thank you for your contribution. Since there has not been recent engagement, we are going to close this out. Feel free to reopen if you'd like to continue working on these changes. Please be sure to remove the no-recent-activity label; otherwise, this is likely to be closed again with the next cleanup pass.