Change eci prefix from upper case to lowercase

[diondrapeck]

Description

This PR changes ECI case from upper to lower to match other evaluator type casing and integrate better with UI evaluation flows.

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.
• I confirm that all new dependencies are compatible with the MIT license.
• 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

• Title of the pull request is clear and informative.
• 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

• Pull request includes test coverage for the included changes.

[github-actions]

promptflow-evals test result

 12 files  ±  0   12 suites  ±0   1h 48m 37s ⏱️ + 1h 31m 28s
 64 tests  -  61   61 ✅  -  64   3 💤 + 3  0 ❌ ±0 
768 runs   - 732  732 ✅  - 768  36 💤 +36  0 ❌ ±0 

Results for commit 6051601. ± Comparison against base commit e79da2e.

This pull request removes 125 and adds 64 tests. Note that renamed tests count towards both.

tests.evals.unittests.test_batch_run_context.TestBatchRunContext ‑ test_batch_timeout_custom
tests.evals.unittests.test_batch_run_context.TestBatchRunContext ‑ test_batch_timeout_default
tests.evals.unittests.test_batch_run_context.TestBatchRunContext ‑ test_with_codeclient
tests.evals.unittests.test_batch_run_context.TestBatchRunContext ‑ test_with_pfclient
tests.evals.unittests.test_built_in_evaluator.TestBuiltInEvaluators ‑ test_fluency_evaluator
tests.evals.unittests.test_built_in_evaluator.TestBuiltInEvaluators ‑ test_fluency_evaluator_empty_string
tests.evals.unittests.test_built_in_evaluator.TestBuiltInEvaluators ‑ test_fluency_evaluator_non_string_inputs
tests.evals.unittests.test_chat_evaluator.TestChatEvaluator ‑ test_conversation_validation_invalid_citations
tests.evals.unittests.test_chat_evaluator.TestChatEvaluator ‑ test_conversation_validation_missing_role
tests.evals.unittests.test_chat_evaluator.TestChatEvaluator ‑ test_conversation_validation_normal
…

tests.evals.e2etests.test_builtin_evaluators.TestBuiltInEvaluators ‑ test_composite_evaluator_chat[False-True]
tests.evals.e2etests.test_builtin_evaluators.TestBuiltInEvaluators ‑ test_composite_evaluator_chat[True-True]
tests.evals.e2etests.test_builtin_evaluators.TestBuiltInEvaluators ‑ test_composite_evaluator_content_safety
tests.evals.e2etests.test_builtin_evaluators.TestBuiltInEvaluators ‑ test_composite_evaluator_content_safety_chat[False-False]
tests.evals.e2etests.test_builtin_evaluators.TestBuiltInEvaluators ‑ test_composite_evaluator_content_safety_chat[True-False]
tests.evals.e2etests.test_builtin_evaluators.TestBuiltInEvaluators ‑ test_composite_evaluator_qa[False]
tests.evals.e2etests.test_builtin_evaluators.TestBuiltInEvaluators ‑ test_composite_evaluator_qa[True]
tests.evals.e2etests.test_builtin_evaluators.TestBuiltInEvaluators ‑ test_composite_evaluator_qa_for_nans
tests.evals.e2etests.test_builtin_evaluators.TestBuiltInEvaluators ‑ test_composite_evaluator_qa_with_openai_config[False]
tests.evals.e2etests.test_builtin_evaluators.TestBuiltInEvaluators ‑ test_composite_evaluator_qa_with_openai_config[True]
…

♻️ This comment has been updated with latest results.