Register seelog log formatter before using it

[amogh09]

Summary

The ECS init service was encountering a "format error: unrecognized formatter at 1: InitLogfmt" error during startup. This occurred because the custom formatter InitLogfmt was being used in the seelog configuration before it was registered with the seelog library. This fixes #4680.

Root Cause Analysis

The issue was in the initialization sequence in the Setup() function in logger/log.go:

1. The function first checked for a log level environment variable and called SetLogLevel()
2. SetLogLevel() internally called reloadConfig(), which tried to use the InitLogfmt formatter
3. Only after this did the code register the formatter with seelog.RegisterCustomFormatter()
4. This timing issue caused the error message to appear during startup

Implementation details

Reordered the initialization sequence in the Setup() function to:

1. Register the custom formatter first, before any logging configuration is loaded
2. Then set the log level from the environment variable if provided
3. If no log level is set, reload the configuration to apply the formatter registration

This ensures that the formatter is registered before any attempt to use it in the logging configuration.

Testing

The fix was tested by:

1. Compiling a new binary with the changes
2. Replacing the existing binary on a running system
3. Verifying that the service starts without the error message
4. Confirming that logging works properly in both the journal and log files

New tests cover the changes: no

Description for the changelog

Fixed "unrecognized formatter" error by registering custom log formatter before loading seelog configuration.

Additional Information

Does this PR include breaking model changes? If so, Have you added transformation functions?

No

Does this PR include the addition of new environment variables in the README?

No

Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.