jit: the JIT runtime entry points get their own file; three AOT emitter fixes

[aleksisch]

Two commits lifted out of #3927 so that PR carries only its own feature.

jit: the runtime entry points JIT code calls move to their own file

src/builtin/module_jit.cpp held two unrelated things: the das module (bindings, linker invocation, emit orchestration) and the set of extern "C" symbols jitted and LLVM-AOT-emitted code links against. The second set moves to src/builtin/jit_runtime.cpp, which registers no module - 2020 lines become 759 + 1265.

A pure move: sorting both files' lines and diffing against the original shows no line removed and no line changed, only the new file's include block, its namespace das { wrapper and the fio forward declarations it repeats.

src/builtin/jit_runtime.h carries the 48 address takers the module binds, so they leave include/daScript/simulate/aot_builtin_jit.h - the header Module_Jit::aotRequire injects into generated AOT C++. They are codegen-time queries that AOT output never calls: modules/dasLLVM/daslib/*.das is outside the AOT glob, and the one generated .cpp that carries the include uses nothing from it. What stays in the public header is the instrumentation API a das program can legitimately call and have AOT-compiled.

The new header opens with the rule that keeps it short: an entry point here is a call boundary the optimizer cannot see through, so an operation that can be expressed as LLVM IR should be, and a runtime entry point is for what cannot.

aot: the C++ emitter qualifies a name, types a lane, and keeps a field's module

Three independent AOT emitter defects:

• a member pointer emitted unqualified, which fails to compile when the member's class is not the enclosing one;
• a vector lane extract emitted untyped, so v_extract_*i fed a signed/unsigned comparison and tripped -Wsign-compare;
• a struct field's module dropped from the used-module walk, so a context could reference a module it never required.

The name table is also cleared before each emission, which a second emission in one process needs.