fix: Update rust composite query to work again (#698)

This PR fixes the rust composite query to work again. Some of the changes:

Move dfx.json in the top level project directory for rust composite queries to not confuse dfx.
Add a Cargo.lock as per usual practice.
Use proper rust targets for the canisters.
Update readme and instructions a bit to build both the data partition and kv_frontend before installing the frontend and running queries against it.

.github/workflows/rust-composite_query-example.yml

@@ -22,13 +22,15 @@ jobs:
         run: bash .github/workflows/provision-darwin.sh
       - name: Rust composite_query Darwin
         run: |
-          dfx start --background
           pushd rust/composite_query
+          dfx start --background
+          dfx canister create data_partition
+          dfx build data_partition
           dfx canister create kv_frontend
           dfx build kv_frontend
           dfx canister install kv_frontend
           dfx canister call kv_frontend put '(1, 1337)'
-          dfx canister call kv_frontend get '(1)' | grep 1337
+          dfx canister call kv_frontend get '(1)' | grep '1_337'
           popd
   rust-composite_query-linux:
     runs-on: ubuntu-20.04
@@ -38,11 +40,13 @@ jobs:
         run: bash .github/workflows/provision-linux.sh
       - name: Rust composite_query Linux
         run: |
-          dfx start --background
           pushd rust/composite_query
+          dfx start --background
+          dfx canister create data_partition
+          dfx build data_partition
           dfx canister create kv_frontend
           dfx build kv_frontend
           dfx canister install kv_frontend
           dfx canister call kv_frontend put '(1, 1337)'
-          dfx canister call kv_frontend get '(1)' | grep 1337
+          dfx canister call kv_frontend get '(1)' | grep '1_337'
           popd