Module identity and once-only bodies

Implement class ReloadableModule demonstrating import-cache semantics: 1. install(name) creates a types.ModuleType(name), sets mod.exec_count = 0, registers it in sys.modules[name], and stores it on self.modules[name]. 2. import_again(name) returns sys.modules[name] WITHOUT re-executing anything. 3. simulate_body_execution(name) increments that module's exec_count += 1 (simulating a module body run). 4. identity_stable(name) returns True when repeated import_again calls always return the SAME object. Graded checks: identity is stable; exec_count only changes when simulate_body_execution is explicitly called — mirroring real import-once semantics.

Difficulty: advanced