Remove jl_task_stack_buffer (#54527)

This was removed previously in PR #54527 but had to be reverted in
PR #54559 as one usage remained (more by accident then by design).
This has since then been resolved.

src/jl_exported_funcs.inc

@@ -449,7 +449,6 @@
     XX(jl_tagged_gensym) \
     XX(jl_take_buffer) \
     XX(jl_task_get_next) \
-    XX(jl_task_stack_buffer) \
     XX(jl_termios_size) \
     XX(jl_test_cpu_feature) \
     XX(jl_threadid) \

src/julia_gcext.h

@@ -135,15 +135,6 @@ JL_DLLEXPORT int jl_gc_conservative_gc_support_enabled(void);
 // NOTE: Only valid to call from within a GC context.
 JL_DLLEXPORT jl_value_t *jl_gc_internal_obj_base_ptr(void *p) JL_NOTSAFEPOINT;
 
-// Return a non-null pointer to the start of the stack area if the task
-// has an associated stack buffer. In that case, *size will also contain
-// the size of that stack buffer upon return. Also, if task is a thread's
-// current task, that thread's id will be stored in *tid; otherwise,
-// *tid will be set to -1.
-//
-// DEPRECATED: use jl_active_task_stack() instead.
-JL_DLLEXPORT void *jl_task_stack_buffer(jl_task_t *task, size_t *size, int *tid);
-
 // Query the active and total stack range for the given task, and set
 // *active_start and *active_end respectively *total_start and *total_end
 // accordingly. The range for the active part is a best-effort approximation

src/task.c

@@ -352,34 +352,6 @@ void JL_NORETURN jl_finish_task(jl_task_t *ct)
     abort();
 }
 
-JL_DLLEXPORT void *jl_task_stack_buffer(jl_task_t *task, size_t *size, int *ptid)
-{
-    size_t off = 0;
-#ifndef _OS_WINDOWS_
-    jl_ptls_t ptls0 = jl_atomic_load_relaxed(&jl_all_tls_states)[0];
-    if (ptls0->root_task == task) {
-        // See jl_init_root_task(). The root task of the main thread
-        // has its buffer enlarged by an artificial 3000000 bytes, but
-        // that means that the start of the buffer usually points to
-        // inaccessible memory. We need to correct for this.
-        off = ROOT_TASK_STACK_ADJUSTMENT;
-    }
-#endif
-    jl_ptls_t ptls2 = task->ptls;
-    *ptid = -1;
-    if (ptls2) {
-        *ptid = jl_atomic_load_relaxed(&task->tid);
-#ifdef COPY_STACKS
-        if (task->ctx.copy_stack) {
-            *size = ptls2->stacksize;
-            return (char *)ptls2->stackbase - *size;
-        }
-#endif
-    }
-    *size = task->ctx.bufsz - off;
-    return (void *)((char *)task->ctx.stkbuf + off);
-}
-
 JL_DLLEXPORT void jl_active_task_stack(jl_task_t *task,
                                        char **active_start, char **active_end,
                                        char **total_start, char **total_end)