Remove legacy bootstrap #2404

Job	Run time
macOS [UBSAN] [lmdb \| clang]	33m 40s
macOS [ASAN] [lmdb \| clang]	29m 33s
Linux [UBSAN] [lmdb \| clang]	39m 5s
macOS [TSAN] [lmdb \| clang]	30m 58s
Linux [ASAN] [lmdb \| clang]	39m 5s
macOS [UBSAN] [rocksdb \| clang]	38m 18s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	41m 6s
Linux [TSAN] [lmdb \| clang]	41m 5s
macOS [ASAN] [rocksdb \| clang]	41m 6s
Linux [LEAK] [lmdb \| clang]	39m 10s
macOS [TSAN] [rocksdb \| clang]	47m 40s
Linux [UBSAN] [rocksdb \| clang]	52m 13s
Linux [ASAN] [rocksdb \| clang]	54m 41s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	54m 56s
Linux [LEAK] [rocksdb \| clang]	58m 57s
	10h 41m 33s

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