feat: expose `returns` field for `DynSolCall` type #2169

Job	Run time
check no_std	40s
clippy	1m 12s
docs	59s
features stable	1m 50s
features stable --all-targets	2m 38s
fmt	12s
miri --no-default-features	5m 28s
miri	5m 28s
features nightly	2m 29s
test ubuntu-latest stable --no-default-features	1m 6s
miri --all-features	7m 42s
features nightly --all-targets	3m 47s
test ubuntu-latest stable	52s
wasm	24s
test ubuntu-latest nightly --no-default-features	1m 19s
test ubuntu-latest nightly	1m 16s
test ubuntu-latest 1.79 --no-default-features	31s
test ubuntu-latest 1.79	28s
test windows-latest stable --no-default-features	2m 38s
test windows-latest stable	2m 37s
test windows-latest nightly --no-default-features	2m 36s
test windows-latest nightly	2m 46s
test windows-latest 1.79 --no-default-features	1m 12s
test windows-latest 1.79	1m 17s
test ubuntu-latest 1.79 --features json	33s
test windows-latest 1.79 --features json	1m 15s
test ubuntu-latest nightly --all-features	1m 26s
test windows-latest nightly --all-features	3m 11s
ci success	3s
	57m 55s

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