Remove legacy bootstrap #2397

Job	Run time
Linux [UBSAN] [lmdb \| clang]	42m 17s
Linux [ASAN] [lmdb \| clang]	42m 51s
macOS [UBSAN] [lmdb \| clang]	34m 46s
macOS [ASAN] [lmdb \| clang]	29m 16s
macOS [TSAN] [lmdb \| clang]	31m 32s
macOS [UBSAN] [rocksdb \| clang]	44m 2s
macOS [ASAN] [rocksdb \| clang]	39m 40s
Linux [ASAN_INT] [lmdb \| clang] (Errors Ignored)	40m 59s
macOS [TSAN] [rocksdb \| clang]	59m 3s
Linux [TSAN] [lmdb \| clang]	44m 40s
Linux [LEAK] [lmdb \| clang]	42m 33s
Linux [UBSAN] [rocksdb \| clang]	51m 19s
Linux [ASAN] [rocksdb \| clang]	56m 33s
Linux [ASAN_INT] [rocksdb \| clang] (Errors Ignored)	59m 11s
Linux [LEAK] [rocksdb \| clang]	57m 29s
	11h 16m 11s

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