Build

Add bindings to backup & restore wallet #31

Job	Run time
build_feature_electrum (linux)	53s
build_all_features (nightly, linux)	42s
build_feature_esplora (linux)	53s
build_feature_electrum (windows)	1m 57s
build_all_features (nightly, windows)	2m 58s
build_feature_electrum (macos)	48s
build_feature_esplora (windows)	3m 25s
build_no_default_features (linux)	39s
build_all_features (nightly, macos)	49s
build_no_default_features (windows)	3m 7s
build_all_features (stable, linux)	40s
build_feature_esplora (macos)	1m 10s
build_all_features (stable, windows)	3m 9s
build_no_default_features (macos)	54s
build_all_features (stable, macos)	46s
build_all_features (1.77.0, linux)	1m 1s
build_all_features (1.77.0, windows)	2m 49s
build_all_features (1.77.0, macos)	1m 18s
	27m 58s

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