Create Gateway service channel factory

[xyuanlu]

Issues

• My PR addresses the following Helix issues and references them in the PR description:

#2821

Description

• Here are some details about my PR, including screenshots of any UI changes:

This PR introduces a new configuration system for the Helix Gateway service, allowing for more flexible and customizable channel configurations. The main changes include:

1. Introduction of GatewayServiceChannelConfig class to manage various channel configurations.
2. Implementation of a factory pattern (HelixGatewayServiceChannelFactory) for creating appropriate service channels based on the configuration.
   The PR also includes various improvements in error handling, logging, and code organization.

Tests

• The following tests are written for this issue:

• GatewayServiceChannelConfigTest: Tests the new GatewayServiceChannelConfig class and its builder.

• TestGatewayServiceConnection: Updated to use the new configuration system.

• TestGatewayServiceManager: Modified to work with the new channel configuration.

(If CI test fails due to known issue, please specify the issue and test PR locally. Then copy & paste the result of "mvn test" to here.)

Changes that Break Backward Compatibility (Optional)

• My PR contains changes that break backward compatibility or previous assumptions for certain methods or API. They include:

(Consider including all behavior changes for public methods or API. Also include these changes in merge description so that other developers are aware of these changes. This allows them to make relevant code changes in feature branches accounting for the new method/API behavior.)

Documentation (Optional)

• In case of new functionality, my PR adds documentation in the following wiki page:

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Commits

• My commits all reference appropriate Apache Helix GitHub issues in their subject lines. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Code Quality

• My diff has been formatted using helix-style.xml
  (helix-style-intellij.xml if IntelliJ IDE is used)

[junkaixue]

overall lgtm. few minor comments.

[junkaixue]

Only one minor refactor. Good job! lgtm

[xyuanlu]

This pr is ready to be merged. Approved by @junkaixue
Commit message:
Create Gateway service channel factory

This PR introduces a new configuration system for the Helix Gateway service, allowing for more flexible and customizable channel configurations. The main changes include:

-Introduction of GatewayServiceChannelConfig class to manage various channel configurations.
-Implementation of a factory pattern (HelixGatewayServiceChannelFactory) for creating appropriate service channels based on the configuration.
-The PR also includes various improvements in error handling, logging, and code organization.