api: first draft for removing nativespec from ImageBuf #6478

Job	Run time
macos-12 appleclang13/C++17 py3.11 MacOS-12	9m 12s
macos-13 appleclang14/C++17 py3.11 MacOS-13	8m 18s
macos-14 appleclang15/C++20 py3.12 MacOS-14-ARM	6m 50s
Ubuntu latest releases gcc13 C++20 py3.12 avx2 exr3.3 ocio2.4	12m 34s
VFX2021 gcc9/C++17 py3.7 exr3.1 ocio2.0	8m 21s
Ubuntu bleeding edge gcc14 C++20 py3.12 OCIO/libtiff/exr-main avx2	5m 4s
windows-2019 VS2019	12m 12s
VFX2021 clang10/C++17 avx2 exr3.1 ocio2.0	9m 19s
Ubuntu all local builds gcc12 C++17 avx2 exr3.2 ocio2.3	12m 5s
windows-2022 VS2022	11m 15s
VFX2022 gcc9/C++17 py39 exr3.1 ocio2.1	7m 7s
Ubuntu clang14 C++20 avx2 exr3.1 ocio2.1	7m 26s
VFX2022 clang13/C++17 py39 avx2 exr3.1 ocio2.1	7m 5s
Ubuntu debug gcc9/C++17, sse4.2, exr3.1	6m 55s
VFX2022 icc/C++17 py3.9 exr3.1 ocio2.1 qt5.15	6m 9s
Ubuntu static libs gcc9 C++17 exr2.4	8m 4s
VFX2022 icx/C++17 py3.9 exr3.1 ocio2.2 qt5.15	9m 33s
Ubuntu clang-format	5m 55s
VFX2024 sanitizers	4m 10s
VFX2023 gcc11/C++17 py3.10 exr3.1 ocio2.2	5m 38s
VFX2024 gcc11/C++17 py3.11 exr3.2 ocio2.3	5m 59s
VFX2021 oldest gcc9.3/C++17 py3.7 exr-3.1	8m 27s
VFX2021 hobbled gcc9.3/C++17 py3.7 exr-3.1 no-sse	8m 27s
VFX2023 abi check	4m 5s
	3h 10m 10s

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