Move TLS-related properties to the separate state object

In the continuation of [this thread](https://github.com/canonical/opensearch-single-kernel-library/pull/24#discussion_r2862613603): it's better to move out all the TLS properties into the distinct `TlsState` object in order to maintain separation of concerns and therefore improve codebase readability.

Start by reading the linked PR #24 discussion and locating the existing TLS properties and TlsState definition in the Python library. Done means all TLS properties are held by TlsState, with the separation of concerns preserved across the affected code.

Written by the indexing model from the issue text.