miniscript/iter: make test module non-pub

We have a `pub mod tests` module which is commented as being public
"in case dependent libraries want to use these functions". However,
it's also gated by #[cfg(test)]. I am not aware of any way that
dependent libraries could compile *this* one with cfg(test) on. So
this module was, in effect, never public.

Make it non-pub to make things clearer, and also to silence all the
"missing docs" warnings that appear when running clippy with --all-targets.

This is NOT an API-breaking change even though it removes a public module,
because the module was never actually usable.

Author: apoelstra

src/miniscript/iter.rs

@@ -222,25 +222,23 @@ impl<'a, Pk: MiniscriptKey, Ctx: ScriptContext> Iterator for PkIter<'a, Pk, Ctx>
     }
 }
 
-// Module is public since it export testcase generation which may be used in
-// dependent libraries for their own tasts based on Miniscript AST
 #[cfg(test)]
-pub mod test {
+mod test {
     use bitcoin;
     use bitcoin::hashes::{hash160, ripemd160, sha256, sha256d, Hash};
     use bitcoin::secp256k1;
 
     use super::Miniscript;
     use crate::miniscript::context::Segwitv0;
 
-    pub type TestData = (
+    type TestData = (
         Miniscript<bitcoin::PublicKey, Segwitv0>,
         Vec<bitcoin::PublicKey>,
         Vec<hash160::Hash>,
         bool, // Indicates that the top-level contains public key or hashes
     );
 
-    pub fn gen_secp_pubkeys(n: usize) -> Vec<secp256k1::PublicKey> {
+    fn gen_secp_pubkeys(n: usize) -> Vec<secp256k1::PublicKey> {
         let mut ret = Vec::with_capacity(n);
         let secp = secp256k1::Secp256k1::new();
         let mut sk = [0; 32];
@@ -258,14 +256,14 @@ pub mod test {
         ret
     }
 
-    pub fn gen_bitcoin_pubkeys(n: usize, compressed: bool) -> Vec<bitcoin::PublicKey> {
+    fn gen_bitcoin_pubkeys(n: usize, compressed: bool) -> Vec<bitcoin::PublicKey> {
         gen_secp_pubkeys(n)
             .into_iter()
             .map(|inner| bitcoin::PublicKey { inner, compressed })
             .collect()
     }
 
-    pub fn gen_testcases() -> Vec<TestData> {
+    fn gen_testcases() -> Vec<TestData> {
         let k = gen_bitcoin_pubkeys(10, true);
         let _h: Vec<hash160::Hash> = k
             .iter()