vm.c: generalize pre-dispatch argument count check for C methods

Replace check_method_noarg() with check_argument_count() that validates
min <= argc <= max using the full aspec stored in mrb_method_t.flags.
This catches ArgumentError earlier at dispatch time, before entering
the C function.

The old check only handled the special case of aspec==0 (NOARG).
The new check extracts REQ, OPT, REST, POST, KEY, and KDICT from
the aspec and validates accordingly. Keyword hash is counted as
a positional arg only when the method doesn't accept keywords.

Remove MRB_METHOD_NOARG_P macro from proc.h (subsumed by aspec check).
Fix 15 incorrect aspec declarations across the codebase that were
exposed by the stricter enforcement.

Co-authored-by: Claude <noreply@anthropic.com>

include/mruby/proc.h

@@ -122,7 +122,6 @@ MRB_API mrb_value mrb_proc_cfunc_env_get(mrb_state *mrb, mrb_int idx);
 #define MRB_METHOD_VISIBILITY_MASK ((1 << 25) | (1 << 26))
 
 #define MRB_METHOD_FUNC_P(m) ((m).flags&MRB_METHOD_FUNC_FL)
-#define MRB_METHOD_NOARG_P(m) (((m).flags&0xffffff)==0)
 #define MRB_METHOD_FUNC(m) ((m).as.func)
 #define MRB_METHOD_FROM_FUNC(m,fn) do{(m).flags=MRB_METHOD_FUNC_FL;(m).as.func=(fn);}while(0)
 #define MRB_METHOD_FROM_PROC(m,pr) do{(m).flags=0;(m).as.proc=(pr);}while(0)