fix: <ranges> support for py::tuple and py::list

[ObeliskGate]

Description

It seems that #4127 has made a mistake there: actually p2325r3 says nothing about C++ sentinels (which always requires semiregular), so it's necessary to add a default constructor for iterator_policies classes.

Moreover, forward_iterator concept requires that:

Value-initialized iterators of the same type may be compared and shall compare equal to other value-initialized iterators of the same type.

and it's tested here:
https://github.com/ObeliskGate/pybind11/blob/74615a04105366647261da83f2980cd5df01b3cd/tests/test_pytypes.cpp#L932-L940
, together with other simple tests.

Suggested changelog entry:

fix and test ``<ranges>`` support for ``py::tuple`` and ``py::list``

[ObeliskGate]

There's two tiny questions:

1. clang had a bug fixed at clang-16 [concepts] deferred substitution into requirements of class template members not implemented llvm/llvm-project#44178, which caused clang with libstdc++ unable to use <ranges>. I've tried to run tests with clang++-15 -fexperimental-library -stdlib=libc++ on my machine, and while the test of <ranges> can pass, another test test_cross_module_exception_translator failed, so I wonder if it's necessary to support it.
2. It seems that there's no CI that test pypy with C++20, and in this situation it will make generic_iterator<iterator_policies::sequence_slow_readwrite> used by list and tuple in pypy not tested, although I'm sure the behavior is right currently.

[rwgk]

[rwgk]

2. It seems that there's no CI that test pypy with C++20

pypy has so many problems and flakes so often, I wouldn't want to add another (flaky) job.

[rwgk]

1. clang had a bug fixed at clang-16 ... so I wonder if it's necessary to support it.

No.

We have so much test coverage across other compilers, we don't need to get that one.

[rwgk]

Looks nice, but caveat: I'm not familiar with <ranges>, std::random_access_iterator, std::ranges::views::transform.

I'll merge this after you condense the code around PYBIND11_TEST_PYTYPES_HAS_RANGES.