Remove ExecutorCompileCheck from plan selection #949

Why

This is un-needed complexity for now.

What

Remove:

• ExecutorCompileCheck, ExecutorCompileError, PlanningModels::executor_compile_check / with_executor_compile_check
• RejectionCause::ExecutorCannotCompile
• PlannerExecutorCompileCheck
• the executor_compile_check condition in components()

Update stage_pipeline, planner_fuzz, tests with stub checkers (search/route.rs, search/refinement/objectives.rs, lib.rs) and docs/develop_docs/library-api.md.