Add custom deleter support to UniquePtr #4837

Job	Run time
Bazel on ${{ (((matrix.os == 'ubuntu') && 'Linux') \|\| ((matrix.os == 'macos') && 'macOS') \|\| ((matrix.os == 'windows') && 'Windows') \|\| '???') }}	0s
Clang Tidy	0s
Outdated	0s
Clippy	0s
Reindeer	0s
pre_ci / pre_ci	1s
Minimal versions	22s
Documentation	24s
Rust nightly	1m 3s
Rust beta	51s
Rust stable	44s
Rust 1.60.0	3m 22s
Rust 1.70.0	57s
Cargo on macOS	1m 59s
Cargo on Windows (msvc)	1m 39s
	11m 22s

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