Add structured version info for readline

Feature or enhancement

readline exposes the version of the readline library only under private names: _READLINE_VERSION (RL_READLINE_VERSION, an int like 0x0803), _READLINE_RUNTIME_VERSION (rl_readline_version, an int) and _READLINE_LIBRARY_VERSION (rl_library_version, a string like '8.3'), added for tests.

Add readline.READLINE_VERSION_INFO for the build-time version and readline.readline_version_info for the runtime version, named tuples with major and minor fields (readline has no third component), and readline.readline_version for the runtime version string. The private names are kept for backward compatibility.

With the libedit backend (readline.backend == 'editline', i.e. the module was built against libedit's readline emulation), these describe the emulated readline API (4.2, 'EditLine wrapper'), not libedit itself, which has no meaningful version API.

Linked PRs

• gh-157486

まず、readline に既存するプライベートなバージョン名と、issue に記載されているバックエンド固有の動作を確認します。要求された名前とフィールドで、ビルド時および実行時の公開バージョン情報が公開され、プライベートな名前が引き続き利用可能であり、libedit の値がそのエミュレートされた API を表していれば完了です。