Add rand feature

Currently we activate the "bitcoin/rand-std" feature unconditionally
in `json`. Some users may not wish to use the bitcoin "rand" feature.

Add a "rand" feature to `json` and `client` and use it to activate
"rand-std" in `bitcoin`.

Author: tcharding

Diff for: client/Cargo.toml

@@ -20,6 +20,7 @@ path = "src/lib.rs"
 
 [features]
 verifymessage = ["bitcoincore-rpc-json/verifymessage"]
+rand = ["bitcoincore-rpc-json/rand"]
 
 [dependencies]
 bitcoincore-rpc-json = { version = "0.18.0", path = "../json" }

Diff for: integration_test/Cargo.toml

@@ -5,7 +5,7 @@ authors = ["Steven Roose <[email protected]>"]
 edition = "2018"
 
 [dependencies]
-bitcoincore-rpc = { path = "../client", features = ["verifymessage"] }
+bitcoincore-rpc = { path = "../client", features = ["verifymessage", "rand"] }
 bitcoin = { version = "0.32.0", features = ["serde", "rand", "base64"]}
 lazy_static = "1.4.0"
 log = "0.4"

Diff for: json/Cargo.toml

@@ -21,9 +21,10 @@ path = "src/lib.rs"
 
 [features]
 verifymessage = ["bitcoin/base64"]
+rand = ["bitcoin/rand-std"]
 
 [dependencies]
 serde = { version = "1.0.156", features = [ "derive" ] }
 serde_json = "1.0.96"
 
-bitcoin = { version = "0.32.0", features = ["serde", "rand-std"] }
+bitcoin = { version = "0.32.0", features = ["serde"] }