Add `finalize` to `Psbt` #1120

Job	Run time
Build and test Manylinux 2.28 x86_64 wheels (cp38-cp38)	3m 41s
Build and test macOS x86_64 wheels (3.8)	4m 36s
Build and test macOS arm64 wheels (3.8)	4m 47s
Build and test macOS x86_64 wheels (3.9)	3m 58s
Build and test Windows wheels (3.8)	5m 46s
Build and test Manylinux 2.28 x86_64 wheels (cp39-cp39)	3m 51s
Build and test macOS arm64 wheels (3.9)	5m 39s
Build and test macOS x86_64 wheels (3.10)	4m 9s
Build and test Windows wheels (3.9)	5m 52s
Build and test Manylinux 2.28 x86_64 wheels (cp310-cp310)	3m 41s
Build and test macOS arm64 wheels (3.10)	4m 24s
Build and test macOS x86_64 wheels (3.11)	5m 35s
Build and test Windows wheels (3.10)	6m 22s
Build and test Manylinux 2.28 x86_64 wheels (cp311-cp311)	3m 43s
Build and test macOS arm64 wheels (3.11)	5m 31s
Build and test macOS x86_64 wheels (3.12)	6m 32s
Build and test Windows wheels (3.11)	5m 56s
Build and test Manylinux 2.28 x86_64 wheels (cp312-cp312)	3m 45s
Build and test macOS arm64 wheels (3.12)	5m 3s
Build and test Windows wheels (3.12)	5m 51s
	1h 38m 42s

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