Make system properties an arbitrary JSON object, plus CI fixes (#349)

* Make system properties an arbitrary JSON object

* Add comment

* Make timestamp test more reliable

* Fmt

* Update src/client.rs

Co-authored-by: David <dvdplm@gmail.com>

* Update src/client.rs

Co-authored-by: David <dvdplm@gmail.com>

* Fix clippy errors and warnings

* Fix tests

Co-authored-by: David <dvdplm@gmail.com>

src/metadata.rs

@@ -143,6 +143,11 @@ pub struct PalletMetadata {
 }
 
 impl PalletMetadata {
+    /// Get the name of the pallet.
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
     /// Encode a call based on this pallet metadata.
     pub fn encode_call<C>(&self, call: &C) -> Result<Encoded, MetadataError>
     where