Finalize 2.0.0 RML toggles and docs

[simonevadi]

Summary

• add per-element RML toggles for reflectivity, slope errors, and alignment errors
• align the beamline-wide Simulate helpers with the per-element toggle behavior
• split the tutorial into dedicated pages and document per-element vs beamline-wide toggles
• finalize the 2.0.0 changelog/version metadata and include the manual RML toggle test assets

Why

Reflectivity could only be toggled beamline-wide, while slope and alignment errors had just gained per-element controls. This change makes the three behaviors consistent at both the element and beamline levels, and updates the docs/tutorial structure to explain the workflow more clearly for 2.0.0.

User impact

Users can now:

• toggle reflectivity_enabled, slope_error_enabled, and alignment_error_enabled on individual supported beamline elements
• keep using Simulate.reflectivity(), Simulate.slope_errors(), and Simulate.alignment_errors() for whole-beamline changes
• follow the new split tutorial pages for manipulation, RAY-UI API usage, simulations, and recipes

Validation

• pytest tests/unit/test_rml_xmltools.py
• python tests/unit/test_simulation_class.py
• python tests/manual_tests/rml_error_toggles/generate_error_toggle_rml.py