build: Check-in Cargo.lock files and lockdown .net (#384)

Use frozen and locked builds

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

.github/workflows/test-ffi.yml

@@ -17,6 +17,7 @@ jobs:
 
       - name: Test FFI
         run: |
-          cargo build -r
+          cargo fetch
+          cargo build -r --frozen
           cargo clippy --all-targets --no-deps -- -Dwarnings
         working-directory: ./bindings/ffi