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Fail loudly on unsupported Optuna parameter distributions

The Optuna suggestion service mapped only UNIFORM and LOG_UNIFORM for int
and double parameters. A parameter declaring NORMAL or LOG_NORMAL fell
through every branch in _get_optuna_search_space and was left out of the
search space, so Optuna never sampled it. The hyperparameter was silently
dropped from tuning with no error or log.

Optuna has no native normal or log-normal distribution, so the backend
cannot honor those values. Add an explicit branch for int and double that
raises a ValueError naming the parameter and distribution, turning a
silent correctness bug into an actionable error. The hyperopt suggestion
service already supports these distributions, so the proto values are
valid input that this backend must reject explicitly rather than ignore.

Adds a parametrized regression test covering NORMAL and LOG_NORMAL for
both int and double parameters.

Fixes #2665

Signed-off-by: Saivedant Hava <saivedant169@gmail.com>