…polyfills (`util/std23.h`) and helpers (`util/helpers.h`)

1c8260c refactor: add `util::to_string(bool)` for convenience (Kittywhiskers Van Gogh)
dec2766 refactor: merge `util/ranges.h` and `util/pointer.h` to `util/helpers.h` (Kittywhiskers Van Gogh)
f57edb5 refactor: use `std23::ranges::fold_left` in Dash-specific code (Kittywhiskers Van Gogh)
4c30be5 util: add polyfill for `std::ranges::fold_left` (Kittywhiskers Van Gogh)
5dc17fc refactor: use `std23::ranges::contains` in Dash-specific code (Kittywhiskers Van Gogh)
43e64ed util: add polyfill for `std::ranges::contains` (Kittywhiskers Van Gogh)
79f0711 refactor: replace `irange::range` with thin `std::views::iota` wrapper (Kittywhiskers Van Gogh)
58a9a3d refactor: switch from `irange(min, max)` to `std::views::iota(min, max)` (Kittywhiskers Van Gogh)
6bee408 refactor: distinguish between custom helpers and polyfills (Kittywhiskers Van Gogh)
f1d5d30 refactor: move `enumerate` to C++23 polyfill, mirror namespace structure (Kittywhiskers Van Gogh)
aa12106 refactor: rename `ToUnderlying()` to match C++23 convention (Kittywhiskers Van Gogh)
2ca0fd7 fix: enum bound check in GetSimulatedErrorRate (Kittywhiskers Van Gogh)

Pull request description:

  ## Motivation

  The upgrade to C++20 ([dash#6380](#6380)) allowed us to drop most of our polyfills meant as bridge from C++17, though we still have utils beyond the ones inherited from upstream that have accumulated over time, most of them, seeking to bridge C++23 features while others are entirely custom or serve as convenience functions or thin wrappers.

  Some of them include:
  * [dash#4622](#4622) for `util/ranges.h` (mostly now an alias to [`std::ranges`](https://en.cppreference.com/w/cpp/ranges.html) after C++20 migration except for `find_if_opt`, which is custom)
  * [dash#4788](#4788) for `util/irange.h` (equivalent to [`std::views::iota`](https://en.cppreference.com/w/cpp/ranges/iota_view.html), introduced in C++20)
  * [dash#5059](#5059) for `util/enumerate.h`  (equivalent to [`std::views::enumerate`](http://en.cppreference.com/w/cpp/ranges/enumerate_view.html), introduced in C++23)
  * [dash#5210](#5210) for `util/underlying.h` (equivalent to [`std::to_underlying`](https://en.cppreference.com/w/cpp/utility/to_underlying.html), introduced in C++23)
  * 0a4e726 for `util/pointer.h` (custom `std::shared_ptr` helper)

  This pull requests compacts all of those helpers into two files:
  * `util/helpers.h` (custom helpers, replacing `util/irange.h`, `util/pointer.h`, `util/ranges.h`)
  * `util/std23.h` (polyfill for C++23, replacing `util/enumerate.h` and `util/underlying.h`)

  And additionally, introduces additional capabilities utilised in Dash-specific code:

  * `std23::ranges::contains` (equivalent to [`std::ranges::contains`](https://en.cppreference.com/w/cpp/algorithm/ranges/contains.html))
  * `std23::ranges::fold_left` (equivalent to [`std::ranges::fold_left`](https://en.cppreference.com/w/cpp/algorithm/ranges/fold_left.html))
  * `util::to_string(bool)` (equivalent to `value ? "true" : "false"`)

  ## Additional Information

  * `ToUnderlying()` needed to be renamed to `to_underlying()` to match with the standard library naming so we can discontinue the polyfill easily when we migrate to C++23 by just going `s/std23/std/g`.

  * While `iranges::range` is equivalent to `std::views::iota`, the latter requires both min and max to be of the same type but literal `0` has a type incompatible with `size_t`, requiring `size_t{0}` to compile. As propagation of these changes for each instance is bothersome, `util::irange()` exists as a thin wrapper that wraps the literal around the type for `max`

  ## Breaking Changes

  None expected.

  ## Checklist

  - [x] I have performed a self-review of my own code
  - [x] I have commented my code, particularly in hard-to-understand areas
  - [x] I have added or updated relevant unit/integration/functional/e2e tests
  - [x] I have made corresponding changes to the documentation **(note: N/A)**
  - [x] I have assigned this pull request to a milestone _(for repository code-owners and collaborators only)_

ACKs for top commit:
  PastaPastaPasta:
    utACK 1c8260c; seems reasonable
  UdjinM6:
    utACK 1c8260c

Tree-SHA512: 82f4b74f304d8680ddb03a923843905a470b374c034284dbe6a013d19e67a769743965f710c5267751742488961907d346ce721d01029cffa543178fd560dcc1