Remove legacy bootstrap #2401

Job	Run time
macOS [UBSAN] [lmdb \| clang]	33m 31s
macOS [ASAN] [lmdb \| clang]	29m 4s
macOS [TSAN] [lmdb \| clang]	31m 25s
macOS [UBSAN] [rocksdb \| clang]	42m 30s
macOS [ASAN] [rocksdb \| clang]	34m 35s
macOS [TSAN] [rocksdb \| clang]	1h 4m 27s
Linux [UBSAN] [lmdb \| clang]	42m 52s
Linux [ASAN] [lmdb \| clang]	41m 48s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	40m 25s
Linux [TSAN] [lmdb \| clang]	43m 1s
Linux [LEAK] [lmdb \| clang]	40m 17s
Linux [UBSAN] [rocksdb \| clang]	51m 4s
Linux [ASAN] [rocksdb \| clang]	54m 26s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	55m 12s
Linux [LEAK] [rocksdb \| clang]	55m 34s
	11h 0m 11s

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