feat: add into_signer to Wallet #563

Job	Run time
test stable --no-default-features	2m 0s
feature-checks	3m 2s
test stable	1m 59s
test stable --all-features	2m 29s
test nightly --no-default-features	2m 26s
wasm	1m 13s
test nightly	2m 21s
test nightly --all-features	2m 26s
test 1.68 --no-default-features	1m 38s
clippy	1m 27s
test 1.68	1m 41s
docs	1m 25s
fmt	14s
	24m 21s

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