Feature: Add function optimizer.load_results() to load OptimizationResults

[ronald-jaepel]

Add function optimizer.load_results() to load and return OptimizationResults based on a checkpoint.h5 or final.h5

[ronald-jaepel]

Tests complete locally but fail on the CI with the same error message as other CI tests:

=========================== short test summary info ============================
FAILED tests/test_cache.py::TestCache::test_delete - sqlite3.OperationalError: no such column: "size" - should this be a string literal in single-quotes?
FAILED tests/test_cache.py::TestCache::test_delete_database - sqlite3.OperationalError: no such column: "size" - should this be a string literal in single-quotes?
FAILED tests/test_cache.py::TestCache::test_get - sqlite3.OperationalError: no such column: "size" - should this be a string literal in single-quotes?
FAILED tests/test_cache.py::TestCache::test_prune - sqlite3.OperationalError: no such column: "size" - should this be a string literal in single-quotes?
FAILED tests/test_cache.py::TestCache::test_set - sqlite3.OperationalError: no such column: "size" - should this be a string literal in single-quotes?
FAILED tests/test_cache.py::TestCache::test_tags - sqlite3.OperationalError: no such column: "size" - should this be a string literal in single-quotes?
FAILED tests/test_optimization_integration.py::TestBatchElutionOptimizationSingleObjective::test_single_core - sqlite3.OperationalError: no such column: "size" - should this be a string literal in single-quotes?
FAILED tests/test_parallelization_adapter.py::TestOptimizerParallelizationBackend::test_parallel_optimization - sqlite3.OperationalError: no such column: "size" - should this be a string literal in single-quotes?