feat: chat UI debug service

[elliotzh]

Description

This PR is targeting to change the experience of Chat UI.

Previously, running pf flow test --ui will generate an url only, which means:

1. need to initialize executor for each request
2. hard to track logs and tracebacks
3. depends on multiple local pfs

Now we will start a monitor on flow directory, which will try to maintain a serve app align with latest flow directory:

1. the serve app won't be restarted unless there are changes in flow definition or init parameters
2. logs and tracebacks will be redirect to the main cli process
3. Chat UI talk to serve app /score directly instead of calling local pfs for each request

Limitations:

1. Signature change in flow definition require manual refresh to update settings tab in Chat UI
2. pf flow serve doesn't support specifying flow file name for now, so give below error message if specified flow file is not picked.
   

basic flex flow chat ui

basic prompty chat ui:

dag flow:

All Promptflow Contribution checklist:

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

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Testing Guidelines

• Pull request includes test coverage for the included changes.

[github-actions]

SDK CLI Test Result zhangxingzhi/flow-test-ui-lifecycle

    4 files      4 suites   1h 3m 48s ⏱️
  737 tests   694 ✅  43 💤 0 ❌
2 948 runs  2 776 ✅ 172 💤 0 ❌

Results for commit 35a41a2.

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[github-actions]

promptflow-core test result

0 tests   0 ✅  0s ⏱️
0 suites  0 💤
0 files    0 ❌

Results for commit 35a41a2.

♻️ This comment has been updated with latest results.

[github-actions]

promptflow SDK CLI Azure E2E Test Result zhangxingzhi/flow-test-ui-lifecycle

  4 files    4 suites   4m 12s ⏱️
243 tests 204 ✅  39 💤 0 ❌
972 runs  816 ✅ 156 💤 0 ❌

Results for commit 35a41a2.

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[github-actions]

SDK CLI Global Config Test Result zhangxingzhi/flow-test-ui-lifecycle

6 tests   6 ✅  1m 25s ⏱️
1 suites  0 💤
1 files    0 ❌

Results for commit 35a41a2.

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[github-actions]

Executor Unit Test Result zhangxingzhi/flow-test-ui-lifecycle

796 tests   796 ✅  3m 45s ⏱️
  1 suites    0 💤
  1 files      0 ❌

Results for commit 35a41a2.

♻️ This comment has been updated with latest results.

[github-actions]

Executor E2E Test Result zhangxingzhi/flow-test-ui-lifecycle

245 tests   239 ✅  5m 2s ⏱️
  1 suites    6 💤
  1 files      0 ❌

Results for commit 35a41a2.

♻️ This comment has been updated with latest results.