[GOBBLIN-2161] Read logExporter classname from config property

[khandelwal-prateek]

Dear Gobblin maintainers,

Please accept this PR. I understand that it will not be reviewed until I have checked off all the steps below!

JIRA

• My PR addresses the following Gobblin JIRA issues and references them in the PR title. For example, "[GOBBLIN-XXX] My Gobblin PR"
  • https://issues.apache.org/jira/browse/GOBBLIN-2161

Description

• Here are some details about my PR, including screenshots (if applicable):
  • This is a follow-up change from [GOBBLIN-2161] Support for configuring openTelemetry metric exporter as logExporter #4061, the change missed reading logExporter classname from the config property metrics.reporting.opentelemetry.logexporter.className's value and was instead reading from config property's key. Fixed it to initialize LogExporter classname from the value in the config.

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• My commits all reference JIRA issues in their subject lines, and I have squashed multiple commits if they address the same issue. 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
  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"