Remove legacy bootstrap #2394

Job	Run time
macOS [UBSAN] [lmdb \| clang]	36m 29s
macOS [ASAN] [lmdb \| clang]	38m 49s
macOS [TSAN] [lmdb \| clang]	36m 29s
Linux [UBSAN] [lmdb \| clang]	40m 2s
macOS [UBSAN] [rocksdb \| clang]	44m 35s
macOS [ASAN] [rocksdb \| clang]	43m 3s
Linux [ASAN] [lmdb \| clang]	41m 29s
macOS [TSAN] [rocksdb \| clang]	54m 30s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	42m 21s
Linux [TSAN] [lmdb \| clang]	41m 14s
Linux [LEAK] [lmdb \| clang]	39m 17s
Linux [UBSAN] [rocksdb \| clang]	50m 19s
Linux [ASAN] [rocksdb \| clang]	53m 21s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	55m 10s
Linux [LEAK] [rocksdb \| clang]	56m 6s
	11h 13m 14s

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