Helm charts - Investigate where importer log files are being created

Summary

groupimport and integrate is dealing with a customer request where the customer is migrating from a GitLab omnibus installation to a Helm-based GitLab instance. They are having issues locating importer relevant log files on the Helm chart, specifically:

• importer.log
• exceptions_json.log

As per a recent Slack discussion (internal only, valid for 90 days), we should deploy the chart, start a migration and force those files to be created.

Next, we should add this information to our docs in https://docs.gitlab.com/ee/administration/logs/#importerlog and https://docs.gitlab.com/ee/administration/logs/#exceptions_jsonlog