Merge rust-bitcoin/rust-bitcoin#1391: `Witness` conversion trait implementations

f0e72dbbfe `Witness` conversion trait impls (Noah Lanson)

Pull request description:

  #1385

  Implemented:
  - `From<Vec<Vec<u8>>>`
  - `From<&[&[u8]]>`
  - `From<&[Vec<u8>]>`
  - `From<Vec<&[u8]>>`

ACKs for top commit:
  tcharding:
    ACK f0e72dbbfe
  Kixunil:
    ACK f0e72dbbfe
  apoelstra:
    ACK f0e72dbbfe

Tree-SHA512: 87e52c62fb76dc41b9b26cc3faf0046598219b7737287961665ccce006e466ca3616b757b3eeff310127c10c1685d2fd897cfc035f1b4acc1fb48ed963e45930

bitcoin/src/blockdata/witness.rs

@@ -457,6 +457,30 @@ impl<'de> serde::Deserialize<'de> for Witness {
     }
 }
 
+impl From<Vec<Vec<u8>>> for Witness {
+    fn from(vec: Vec<Vec<u8>>) -> Self {
+        Witness::from_slice(&vec)
+    }
+}
+
+impl From<&[&[u8]]> for Witness {
+    fn from(slice: &[&[u8]]) -> Self {
+        Witness::from_slice(slice)
+    }
+}
+
+impl From<&[Vec<u8>]> for Witness {
+    fn from(slice: &[Vec<u8>]) -> Self {
+        Witness::from_slice(slice)
+    }
+}
+
+impl From<Vec<&[u8]>> for Witness {
+    fn from(vec: Vec<&[u8]>) -> Self {
+        Witness::from_slice(&vec)
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;