Upgrade environment variable logic using new Pipeline API for logtail environment configuration management

[quzard]

This commit introduces an enhanced file discovery mechanism by transitioning from the old configuration API to the new Pipeline configuration API for ilogtail. With this upgrade, users will experience a change in the way recursive directory scanning is handled.

Previously, the recursive discovery of files within a directory was implied. However, to align with the new API's capabilities and to provide users with explicit control, the recursive behavior must now be explicitly specified in the path configuration.

To enable recursive file discovery within a directory, users should add /**/ at the point in the path where recursion is desired. This syntax will trigger a recursive scan with a maximum depth of 10 levels. If a non-recursive file discovery is required, users should use a single / in the path configuration.

Example usage:

• To recursively discover files: /var/log/myapp/**/app.log
• For non-recursive discovery: /var/log/myapp/app.log

Please note that if you rely on the recursive file discovery feature, you'll need to update your configuration to continue using this functionality with the new Pipeline API.