Add `ElectrumClient::server_features` method #1176

Job	Run time
Build and test macOS arm64 wheels (3.8)	5m 44s
Build and test Manylinux 2.28 x86_64 wheels (cp38-cp38)	4m 5s
Build and test Windows wheels (3.8)	6m 9s
Build and test macOS x86_64 wheels (3.8)	6m 14s
Build and test Manylinux 2.28 x86_64 wheels (cp39-cp39)	3m 54s
Build and test Windows wheels (3.9)	6m 1s
Build and test macOS x86_64 wheels (3.9)	5m 35s
Build and test Manylinux 2.28 x86_64 wheels (cp310-cp310)	3m 49s
Build and test macOS arm64 wheels (3.9)	7m 0s
Build and test Windows wheels (3.10)	6m 7s
Build and test macOS x86_64 wheels (3.10)	5m 44s
Build and test Manylinux 2.28 x86_64 wheels (cp311-cp311)	3m 44s
Build and test macOS arm64 wheels (3.10)	6m 10s
Build and test Windows wheels (3.11)	6m 2s
Build and test macOS x86_64 wheels (3.11)	7m 5s
Build and test Windows wheels (3.12)	6m 27s
Build and test Manylinux 2.28 x86_64 wheels (cp312-cp312)	4m 23s
Build and test macOS arm64 wheels (3.11)	6m 7s
Build and test macOS x86_64 wheels (3.12)	5m 34s
Build and test macOS arm64 wheels (3.12)	9m 23s
	1h 55m 17s

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