Rust

Add `Point::serialized_len` #367

Job	Run time
check-all	43s
check	57s
build-wasm-nostd	33s
build-wasm	4m 37s
check-alloc	16s
check-changelog	5s
check-doc	45s
check-nostd	17s
check-semver (generic-ec, all-features)	2m 37s
clippy	38s
check-semver (generic-ec, only-explicit-features)	2m 34s
clippy-nostd	27s
clippy-tests	43s
check-semver (generic-ec-core, all-features)	2m 32s
fmt	2m 3s
test	2m 10s
check-semver (generic-ec-core, only-explicit-features)	2m 23s
check-semver (generic-ec-curves, all-features)	2m 42s
check-semver (generic-ec-curves, only-explicit-features)	2m 32s
check-semver (generic-ec-zkp, all-features)	2m 31s
check-semver (generic-ec-zkp, only-explicit-features)	3m 2s
	35m 7s

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