PyROS Add caching for computed uncertain parameter bounds

[jas-yao]

Fixes

_fbbt_parameter_bounds in uncertainty_sets.py

Summary/Motivation:

PyROS solves optimization bounding problems for every uncertain parameter multiple times throughout its routine using _compute_exact_parameter_bounds. There are up to 4 instances of PyROS accessing this method during its runtime.

1. Validation in is_bounded. This occurs when no parameter bounds are provided and FBBT fails to find bounds. Only the bounds that FBBT has not found are evaluated.
2. Validation in is_nonempty. This occurs for intersection, polyhedral, and custom uncertainty sets, where a feasibility problem is constructed.
3. Preprocessing in get_effective_uncertain_dimensions if parameter bounds are not provided or the provided ones are not exact.
4. Separation problem construction in add_uncertainty_set_constraints if no parameter bounds are provided.

The time taken to repeatedly solve these bounding problems may add up and be significant for larger uncertainty sets.

This PR adds a method for caching the solutions of these bounding problems so that subsequent processes do not need to solve the bounding problems again.

This PR also fixes a small bug in _fbbt_parameter_bounds where the returned bounds are not scalar (e.g., a binary variable m.Var = pyo.Var(within=pyo.Binary, bounds=(0,1)) or a binary variable in a model that FBBT has been used on).

Changes proposed in this PR:

• Add a _solve_bounds_optimization method that uses functools.cache to cache solutions for bounding problems solved for any uncertain parameter that is used by _compute_exact_parameter_bounds
• Add a line for clearing the _solve_bounds_optimization cache during validation, which is run at the start of every PyROS solve.
• Add tests for check caching behavior of _solve_bounds_optimization
• Fix the issue in _fbbt_parameter_bounds

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[jas-yao]

@shermanjasonaf @jsiirola