Add `ElectrumClient::server_features` method #1182

Job	Run time
Build and test macOS arm64 wheels (3.8)	6m 19s
Build and test macOS arm64 wheels (3.9)	9m 35s
Build and test macOS arm64 wheels (3.10)	6m 25s
Build and test macOS arm64 wheels (3.11)	5m 52s
Build and test macOS arm64 wheels (3.12)	7m 22s
Build and test macOS x86_64 wheels (3.8)	7m 55s
Build and test macOS x86_64 wheels (3.9)	5m 25s
Build and test macOS x86_64 wheels (3.10)	7m 39s
Build and test macOS x86_64 wheels (3.11)	8m 15s
Build and test macOS x86_64 wheels (3.12)	7m 36s
Build and test Manylinux 2.28 x86_64 wheels (cp38-cp38)	3m 46s
Build and test Manylinux 2.28 x86_64 wheels (cp39-cp39)	3m 46s
Build and test Manylinux 2.28 x86_64 wheels (cp310-cp310)	3m 45s
Build and test Windows wheels (3.8)	5m 27s
Build and test Manylinux 2.28 x86_64 wheels (cp311-cp311)	3m 47s
Build and test Windows wheels (3.9)	5m 39s
Build and test Manylinux 2.28 x86_64 wheels (cp312-cp312)	3m 52s
Build and test Windows wheels (3.10)	5m 48s
Build and test Windows wheels (3.11)	6m 20s
Build and test Windows wheels (3.12)	5m 43s
	2h 0m 16s

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