re-organize analysis module

This sequence of commits reorganizes the rt.restructuring.analysis module as follows.

• rt.restructuring.results — instead of having high-level results in the analysis module, there's now a new top-level module exclusively for main results.
• analysis.abstract — abstract RTA
• analysis.concepts — reserved for definitions of key analysis concepts that are well-known in the literature (e.g., busy window, priority inversion).
• analysis.definitions — all other auxiliary definitions used in the analysis (i.e., minor stuff and technicalities that we need, but that readers are unlikely to be interested in specifically).
• analysis.transform — schedule transformation definitions (this will grow over time with things like suspension-oblivious reduction, overhead accounting reductions, etc.)
• analysis.facts — where all the lemmas live
• analysis.facts.behavior — all basic facts that follow directly from the trace-based semantics
• analysis.facts.* — various lemmas and proofs (this will grow over time and eventually need more structure, but for now it's not clear what this structure should be)