[pydrake] Port the common-init module to nanobind

[jwnimmer-tri]

All other parts of pydrake depend on this module, so it needs to be the first thing ported.

Towards #21572.

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This change is 

[jwnimmer-tri]

+a:@rpoyner-tri for co-author / co-feature review, please, when time allows.

@jwnimmer-tri reviewed 29 files and all commit messages, and made 4 comments.
Reviewable status: LGTM missing from assignee rpoyner-tri(platform), needs at least two assigned reviewers (waiting on rpoyner-tri).

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bindings/pydrake/symbolic_types_pybind.h line 39 at r1 (raw file):

    const uint8_t var_type = static_cast<uint8_t>(hi);
    if (var_type > static_cast<uint8_t>(Variable::Type::RANDOM_EXPONENTIAL)) {
      return std::nullopt;

FYI nanobind requires its type-casters to be noexcept, so we can't provide a more specific error message for invalid arguments like we had with pybind11. Instead, the user will be get a TypeError on the call. The test has been updated to reflect this.

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bindings/pydrake/common/BUILD.bazel line 420 at r1 (raw file):

drake_py_unittest(
    name = "eigen_pybind_test",
    # TODO(#21572) Remove this opt-out.

FYI This pull request only ports the essential components of the init module and any helper libraries required by it.

Higher-layer helper modules that are only needed by other modules in pydrake remain as future work, with TODOs on their tests.

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bindings/pydrake/common/serialize_pybind.h line 151 at r1 (raw file):

    };
    if constexpr (std::is_same_v<T, bool>) {
      return type_of(py::bool_(false));

FYI The nanobind default constructors for primitives like bool_, int_, float_ etc construct None rather than 0, so we need to pass a non-None value here.