chore: add _feature to Variable protos for encoding/decoding from WASM Bucketing

Author: kaushalkapasi

.github/workflows/run-test-harness.yml

@@ -16,5 +16,4 @@ jobs:
         with:
           sdks-to-test: java
           sdk-github-sha: ${{github.event.pull_request.head.sha}}
-          github-token: ${{ secrets.TEST_HARNESS_GH_SECRET }}
-          sdk-capabilities: '["cloud", "edgeDB", "clientCustomData", "v2Config", "allFeatures", "allVariables", "evalReason", "eventsEvalReason", "cloudEvalReason"]'
+          sdk-capabilities: '{ "Java": ["cloud", "edgeDB", "clientCustomData", "v2Config", "allVariables", "allFeatures", "variablesFeatureId", "evalReason", "cloudEvalReason", "eventsEvalReason"]}'

src/main/proto/variableForUserParams.proto

@@ -70,6 +70,7 @@ message SDKVariable_PB {
   double doubleValue = 5;
   string stringValue = 6;
   NullableString evalReason = 7;
+  NullableString _feature = 8; 
   EvalReason_PB eval = 9;
 }