refactor const_sv2 to std logic

protocols/v2/const-sv2/Cargo.toml

@@ -14,13 +14,15 @@ keywords = ["stratum", "mining", "bitcoin", "protocol"]
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-secp256k1 = { version = "0.28.2", default-features = false, features =["hashes", "alloc","rand","rand-std"] }
+secp256k1 = { version = "0.28.2", default-features = false, features = ["hashes", "rand"] }
 
 #[dev-dependencies]
 #cbindgen = "0.16.0"
 
 [features]
-no_std = []
+default = ["std"]
+alloc = ["secp256k1/alloc"]
+std = ["alloc", "secp256k1/rand-std"]
 
 [package.metadata.docs.rs]
 all-features = true

protocols/v2/const-sv2/src/lib.rs

@@ -36,7 +36,7 @@
 //! `channel_id`. In this case, the first 4 bytes of the payload represent the
 //! `channel_id` the message is destined for.
 
-#![cfg_attr(feature = "no_std", no_std)]
+#![cfg_attr(not(feature = "std"), no_std)]
 
 /// Identifier for the extension_type field in the SV2 frame, indicating no
 /// extensions.