testing: improve Ptex testing #6933

Job	Run time
(old) VP2021 gcc9/C++17 py3.7 exr3.1 ocio2.0	15m 44s
(old) VP2021 clang10/C++17 avx2 exr3.1 ocio2.0	16m 20s
(old) VP2022 gcc9/C++17 py39 exr3.1 ocio2.1	15m 43s
(old) VP2022 clang13/C++17 py39 avx2 exr3.1 ocio2.1	15m 12s
(old) oldest gcc9.3/C++17 py3.7 exr-3.1	16m 52s
(old) hobbled gcc9.3/C++17 py3.7 exr-3.1 no-sse	16m 31s
ABI check / c++17 py3.11	12m 18s
all local builds gcc12 C++17 avx2 exr3.2 ocio2.3 / g++-12 c++17 py3.10	19m 15s
bleeding edge gcc14 C++20 py3.12 OCIO/libtiff/exr-main avx2 / g++-14 c++20 py3.12	16m 58s
clang14 C++20 avx2 exr3.1 ocio2.1 / clang++ c++20 py3.8	14m 38s
clang-format / c++17 py3.10	8m 32s
debug gcc9/C++17, sse4.2, exr3.1 / g++-9 c++17 py3.8	19m 8s
latest releases gcc13 C++20 py3.12 avx2 exr3.3 ocio2.4 / g++-13 c++20 py3.12	17m 25s
static libs gcc9 C++17 exr3.1 / g++-9 c++17 py3.8	15m 12s
VFX2023 gcc11/C++17 py3.10 exr3.1 ocio2.2 / c++17 py3.10	11m 31s
VFX2023 icc/C++17 py3.10 exr3.1 ocio2.1 qt5.15 / c++17 py3.10	20m 47s
VFX2023 icx/C++17 py3.10 exr3.1 ocio2.2 qt5.15 / icpx c++17 py3.10	14m 41s
VFX2024 clang/C++17 py3.11 exr3.2 ocio2.3 / clang++ c++17 py3.11	11m 53s
VFX2024 gcc11/C++17 py3.11 exr3.2 ocio2.3 / c++17 py3.11	12m 46s
MacOS-14-ARM aclang15/C++20/py3.12 / clang++ c++20 py3.12	9m 9s
MacOS-13-Intel aclang14/C++17/py3.11 / clang++ c++17 py3.11	30m 11s
VFX2024 sanitizers / clang++ c++17 py3.11	40m 12s
MacOS-15-ARM aclang16/C++20/py3.13 / clang++ c++20 py3.13	10m 8s
Windows-2022 VS2022 / c++17 py3.9	40m 44s
Windows-2019 VS2019 / c++17 py3.7	50m 19s
	7h 52m 9s

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