Merge rust-bitcoin/rust-bitcoincore-rpc#337: Depend on bitcoin v0.32.0 #396

Job	Run time
Test - 1.56.1 toolchain (minimal)	2m 53s
Integration tests - stable toolchain (0.18.0)	1m 22s
Test - 1.56.1 toolchain (recent)	2m 51s
Integration tests - stable toolchain (0.18.1)	1m 2s
Test - nightly toolchain (minimal)	42s
Integration tests - stable toolchain (0.19.0.1)	57s
Test - nightly toolchain (recent)	42s
Integration tests - stable toolchain (0.19.1)	58s
Test - stable toolchain (minimal)	41s
Integration tests - stable toolchain (0.20.0)	1m 2s
Test - stable toolchain (recent)	45s
Integration tests - stable toolchain (0.20.1)	58s
Integration tests - stable toolchain (0.21.0)	59s
	15m 52s

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