Add two new private APIs: _PyObject_LookupAttr() and _PyObject_LookupAttrId()

Affected classes are bytearray, array, deque, defaultdict, count and repeat.

the bare METH_FASTCALL be used for functions with positional-only
parameters.

when pass indices of wrong type.

Issue #29452: Use METH_FASTCALL calling convention for index(), insert() and
rotate() methods of collections.deque to avoid the creation a temporary tuple
to pass position arguments. Speedup on deque methods:

* d.rotate(): 1.10x faster
* d.rotate(1): 1.24x faster
* d.insert(): 1.18x faster
* d.index(): 1.24x faster

* Indent versionchanged at method level, not class level
* Mark up ``--help`` to avoid generating an en dash
* Use forward slash in Unix command line with a dollar sign ($) prompt

Replace
   _PyObject_CallArg1(func, arg)
with
   PyObject_CallFunctionObjArgs(func, arg, NULL)

Using the _PyObject_CallArg1() macro increases the usage of the C stack, which
was unexpected and unwanted. PyObject_CallFunctionObjArgs() doesn't have this
issue.

Replace
    PyObject_CallFunction(func, "O", arg)
and
    PyObject_CallFunction(func, "O", arg, NULL)
with
    _PyObject_CallArg1(func, arg)

Replace
    PyObject_CallFunction(func, NULL)
with
    _PyObject_CallNoArg(func)

_PyObject_CallNoArg() and _PyObject_CallArg1() are simpler and don't allocate
memory on the C stack.

PyDict_GetItemWithError().  Patch by Xiang Zhang.

Don't pass "()" format to PyObject_CallXXX() to call a function without
argument: pass NULL as the format string instead. It avoids to have to parse a
string to produce 0 argument.

and better generated code (on both GCC and CLang).

and for better code generation.

* Add comment to the maxlen structure entry about the meaning of maxlen == -1
* Factor-out code common to deque_append(left) and deque_extend(left)
* Factor inner-loop in deque_clear() to use only 1 test per loop instead of 2
* Tighten inner-loops for deque_item() and deque_ass_item() so that the
  compiler can combine the decrement and test into a single step.

Old code is correct, but with Py_SETREF and Py_CLEAR it can be cleaner.
This patch doesn't fix bugs and hence there is no need to backport it.

This allows sys.getsize() to work correctly with their subclasses with
__slots__ defined.