[3.14] gh-128627: Use __builtin_wasm_test_function_pointer_signature for Emscripten trampoline (GH-137470) (#139039)

gh-128627: Use __builtin_wasm_test_function_pointer_signature for Emscripten trampoline (GH-137470)

With https://github.com/llvm/llvm-project/pull/150201 being merged, there is
now a better way to generate the Emscripten trampoline, instead of including
hand-generated binary WASM content. Requires Emscripten 4.0.12.
(cherry picked from commit 2629ee4eb0e9f66f28772cb4b4cc44ebe6de79ad)

Co-authored-by: Hood Chatham <roberthoodchatham@gmail.com>