Fix config Overloading & its tests

[coolwednesday]

• Currently, we are using Overload for overriding. This causes the system environment variables to be overwritten. To handle this, we now run a manual loop that skips all environment variables initially loaded from the system.

[Umang01-hash]

@coolwednesday I feel the code can be refactored into a simpler implementation. The three file loading functions (loadBaseEnvFile, loadLocalOverrideFile, loadEnvSpecificFile) contain significant duplication - consider creating a generic loadEnvFile function that handles common loading logic and error handling.

[coolwednesday]

@aryanmehrotra, Here is the running tested server :