Support overriding core module with custom implementation

[setiah]

Is your feature request related to a problem? Please describe.
OpenSearch provides some features outside of server as modules and plugins. Modules, like plugins, provide additional functionality on top of core, but cannot be uninstalled. Modules provide a good way to keep the code decoupled from server, yet packaged with every distribution. However, it restricts the user to use the module provided implementation of the featureas there is no way to override a module with custom functionality. There are some use cases like inbuilt security module, which provides security features applicable for every distribution, where users might want to override the module with their own custom implementation.

By overriding, the intent is to only load the classes for custom implementation at the time of bootstrapping OpenSearch process.

Describe the solution you'd like
Provide a mechanism in OpenSearch to override a module with custom implementation via user-provided plugin.

Feedback required
Besides security, are there any more use-cases that could use this framework? Basically, any more use cases where users would like to override some of the existing modules in OpenSearch with a custom implementation at runtime?