fix(_comp_count_args): exclude <>& from wordbreaks as _comp_initialize

In the current implementation, to count the number of arguments, we
reassemble `cword` and `words` by specified exclude chars (i.e.,
characters that should not be considered word breaks even though they
are in COMP_WORDBREAKS).  The reassembly by the top-level
`_comp_initialize` always specify `<>&` as exclude chars, but the
current implementaion of `_comp_count_args` do not specify them.  This
patch specifies `<>&` for `_comp_count_args` in accordance with
`_comp_initialize`.

bash_completion

@@ -2221,7 +2221,7 @@ _comp_get_first_arg()
 _comp_count_args()
 {
     local i cword words
-    _comp__reassemble_words "${1-}" words cword
+    _comp__reassemble_words "${1-}<>&" words cword
 
     ret=1
     for ((i = 1; i < cword; i++)); do

test/t/unit/test_unit_count_args.py

@@ -13,7 +13,7 @@ def _test(self, *args, **kwargs):
         )
 
     def test_1(self, bash):
-        assert_bash_exec(bash, "COMP_CWORD= _comp_count_args")
+        assert_bash_exec(bash, "COMP_LINE= COMP_POINT=0 COMP_WORDS=() COMP_CWORD=; _comp_count_args")
 
     def test_2(self, bash):
         """a b| should set args to 1"""