lightningd: summary plugin addition

- copy only summary plugin folder
- add runtime dependency pyln-client
- update config assets
Signed-off-by: Lakshya Singh <lakshay.singh1108@gmail.com>

assets/testnet-config

@@ -6,4 +6,5 @@ log-level=info
 max-locktime-blocks=288
 important-plugin=/usr/bin/clboss
 clboss-auto-close=true
-bind-addr=0.0.0.0:19735
+bind-addr=0.0.0.0:19735
+plugin=/usr/local/src/plugins/summary/summary.py