[Connection] Support flexflow with connection config

[brynn-code]

Description

• Change connection provider config key to "PF_CONNECTION_PROVIDER" to align with serving existing one.
• Refine connection provider behavior: Let dict connection provider raise error when not found, related executor logic changed.
• Set env var in pfclient, to support flex flow with global config.
• Let default azure credential exclude interactive browser: to avoid unexpected hang up when getting connection inside executor sub process.

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.

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 SDK CLI Azure E2E Test Result brynn/refine-connection-provider-usage

  4 files    4 suites   5m 5s ⏱️
238 tests 203 ✅  35 💤 0 ❌
952 runs  812 ✅ 140 💤 0 ❌

Results for commit e856bcb.

♻️ This comment has been updated with latest results.

[github-actions]

SDK CLI Global Config Test Result brynn/refine-connection-provider-usage

6 tests   6 ✅  1m 14s ⏱️
1 suites  0 💤
1 files    0 ❌

Results for commit e856bcb.

♻️ This comment has been updated with latest results.

[github-actions]

promptflow-core test result

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

Results for commit e856bcb.

♻️ This comment has been updated with latest results.

[github-actions]

Executor Unit Test Result brynn/refine-connection-provider-usage

792 tests   792 ✅  3m 43s ⏱️
  1 suites    0 💤
  1 files      0 ❌

Results for commit e856bcb.

♻️ This comment has been updated with latest results.

[github-actions]

Executor E2E Test Result brynn/refine-connection-provider-usage

241 tests   236 ✅  5m 13s ⏱️
  1 suites    5 💤
  1 files      0 ❌

Results for commit e856bcb.

♻️ This comment has been updated with latest results.

[github-actions]

SDK CLI Test Result brynn/refine-connection-provider-usage

    4 files      4 suites   58m 12s ⏱️
  663 tests   650 ✅ 13 💤 0 ❌
2 652 runs  2 600 ✅ 52 💤 0 ❌

Results for commit e856bcb.

♻️ This comment has been updated with latest results.