[ENH] Add callback support for BaseOptimizer and BaseExperiment

[AdityaPandeyCN]

This PR aims to address #158 and plans to add callback hooks to BaseExperiment.evaluate and BaseOptimizer.solve, configurable via set_config.

Callback hooks:

• callbacks_pre / callbacks_post for experiment evaluations
• callbacks_pre_solve / callbacks_post_solve for optimizer runs

Built-in callbacks:

• HistoryCallback: records params, result, metadata for each evaluation
• LoggingCallback: logs evaluations to console or logger
• SleepCallback: adds delay after evaluations (for testing/simulation)
• TargetReachedCallback: tracks if a target score has been reached

[AdityaPandeyCN]

@SimonBlanke Can you have a look if time permits?