CI: add tests-vendor.yaml for vendor crate testing

Add a new workflow to test vendored crates. Initially includes tests
for the redux crate.

Author: dannywillems

.github/workflows/tests.yaml

@@ -294,6 +294,7 @@ jobs:
               --exclude mina-archive-breadcrumb-compare \
               --exclude webrtc-sniffer
               # --exclude mina-tree
+              # --exclude redux-rs
               # --exclude vrf
 
   account-tests: