Allow collapsing ops with index semantics #35003

Job	Run time
setup / setup	5s
runtime :: ubuntu-24.04	1m 14s
runtime :: ubuntu-24.04-arm	2m 46s
runtime :: windows-2022	3m 18s
runtime_small	2m 16s
runtime :: macos-14	1m 12s
runtime_tracing :: ubuntu-24.04 :: tracy	56s
runtime_tracing :: ubuntu-24.04 :: console	56s
runtime_tracing :: ubuntu-24.04-arm :: tracy	2m 30s
runtime_tracing :: ubuntu-24.04-arm :: console	2m 40s
runtime_tracing :: windows-2022 :: tracy	2m 39s
runtime_tracing :: windows-2022 :: console	2m 40s
runtime_tracing :: macos-14 :: tracy	1m 11s
runtime_tracing :: macos-14 :: console	1m 11s
linux_x64_bazel / linux_x64_bazel	35m 10s
linux_x64_clang / linux_x64_clang	15m 7s
linux_x64_clang_asan / linux_x64_clang_asan	35m 56s
ci_summary / summary	2s
	1h 51m 49s

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