[FEA] `raft-ann-bench` should validate configurations

Is your feature request related to a problem? Please describe.

Currently, the data models for the configuration yaml files are not validated. Directly referencing dict by key isn't safe. For example, in the following code snippet, a typo like constraint instead of constraints in the yaml file could lead to the constraints being ignored silently.

            def add_algo_group(group_list):
                if algo["name"] not in algos_conf:
                    algos_conf[algo["name"]] = {"groups": {}}
                for group in algo["groups"].keys():
                    if group in group_list:
                        algos_conf[algo["name"]]["groups"][group] = algo[
                            "groups"
                        ][group]
                if "constraints" in algo:
                    algos_conf[algo["name"]]["constraints"] = algo[
                        "constraints"
                    ]

Describe the solution you'd like

Use Pydantic to define and validate the data model for the configuration files.

Describe alternatives you've considered

dataclasses.dataclass would work as well.

Start in python/raft-ann-bench/src/raft-ann-bench/run/main.py at the configuration handling around lines 485-496, then trace the YAML data consumed there. Define validation models using Pydantic for the configuration structures and replace unsafe dictionary access; done means configuration typos such as constraint are reported instead of silently ignored.