feat: Separation of examples into different folders to avoid confusion

[azygadlo]

Feature description

Currently, all document search examples such as evaluate.py, ingest.py and optimize.py are stored in the same folder. Their configs also share the same directory. I would suggest to have separate folders for evaluation and optimization examples (in future, if we have multiple evaluation examples, each of them should have a separate subfolder).

We also want to keep an index of existing examples in README file and also mention level of example complexity there.

Motivation

I want to avoid confusion in familiarization with examples. I believe better example separation would help.

Additional context

No response