Replace custom Bls wrapper

[ltitanb]

Regarding

commit-boost-client/crates/common/src/signer/schemes/bls.rs

Lines 16 to 31 in 0f73544

	// TODO(David):
	// This wrapper type is potentially a temporary solution, merely to implement
	// `TreeHash`. Remove when progress is made on this issue (https://github.com/sigp/tree_hash/issues/22)
	// or refine the boundaries between our wrapper `BlsPublicKey` type
	// and alloy's `BlsPublicKey` if we stick with it
	// std traits
	#[derive(Debug, Clone, Copy, LowerHex, Display, PartialEq, Eq, Hash, Default)]
	// serde, ssz, tree_hash
	#[derive(Serialize, Deserialize, TreeHash)]
	#[serde(transparent)]
	// derive_more
	#[derive(Deref, From, Into)]
	pub struct BlsPublicKey {
	inner: BlsPublicKeyInner,
	}

Now tree_hash has a native implementation for [u8; 48]

https://github.com/sigp/tree_hash/blob/e9708cdf80e35c86f9da5f68c6497a9ca2fe5a0e/tree_hash/src/impls.rs#L88-L106

[ltitanb]

ref sigp/tree_hash#22