WIP: Refactoring certs and volumes for sts

[sergeimonakhov]

This pull request introduces code changes related to managing volumes for the STS object. Key modifications include the addition of structures to store certificate information and the definition of paths to certificate files. Additionally, changes have been made to the creation and mounting of the data volume for the ETCD container. These alterations aim to enhance certificate handling and data management within the controller's context.

[sircthulhu]

@sergeimonakhov Please run make lint-fix to resolve pre-commit errors and fix tests

[sergeimonakhov]

@sircthulhu I added even more refactoring and fixed the code to make the tests run. Overall, the base code was very poor; we need to be more stringent in our code reviews because it will become impossible to maintain if we keep accepting sloppy work.

[kvaps]

closed in favor https://github.com/aenix-io/etcd-operator/issues/224