fix(handler): allow CORS in v2 compatibility endpoints

[sranka]

Closes #18391

Describe your proposed changes here.

• add CORS handling so that the web browser clients can access v2 compatibility endpoints as they already can against InfluxDB v2 (fix(CORS): stop processing in pre-flight CORS requests #17640)
• cherry-pick and merge /health v2 compatibility endpoint to the master-1.x branch from 1.8 branch (feat(handler): Add 2.0 compatible health endpoint #17252)

See influxdata/influxdb-client-js#199 to know more.

• CHANGELOG.md updated with a link to the PR (not the Issue)
• Well-formatted commit messages
• Rebased/mergeable
• Tests pass
• Signed CLA (if not already signed)

[sranka]

With these changes, the browser example works fine (write, query, health) also when using a non-proxy influxdb URL (http://localhost:8086).

[sranka]

@dgnorton can you pls re-approve and merge, I only updated the CHANGELOG.md as requested in the issue's template ... but that dismissed your previous review. Updating CHANGELOG.md in pull requests comes with merging and approval problems for contributors with limited rights.