[gRPC/iOS] tvOS unit test fix and pass defs (#29858)

Fixing tvOS unit test build break and passing in interop test server addr via GCC_PREPROCESSOR_DEFINITIONS.
Previously this is passed directly via xcodebuild predefines but it is not visible to TestCommon lib

src/objective-c/tests/Tests.xcodeproj/project.pbxproj

@@ -1263,9 +1263,6 @@
 				GCC_PREPROCESSOR_DEFINITIONS = (
 					"DEBUG=1",
 					"$(inherited)",
-					"HOST_PORT_LOCALSSL=$(HOST_PORT_LOCALSSL)",
-					"HOST_PORT_LOCAL=$(HOST_PORT_LOCAL)",
-					"HOST_PORT_REMOTE=$(HOST_PORT_REMOTE)",
 					"GRPC_TEST_OBJC=1",
 				);
 				GCC_SYMBOLS_PRIVATE_EXTERN = NO;

src/objective-c/tests/Tests.xcodeproj/xcshareddata/xcschemes/TvTests.xcscheme

@@ -65,26 +65,11 @@
          </BuildableReference>
       </MacroExpansion>
       <EnvironmentVariables>
-         <EnvironmentVariable
-            key = "HOST_PORT_LOCAL"
-            value = "localhost:5050"
-            isEnabled = "YES">
-         </EnvironmentVariable>
-         <EnvironmentVariable
-            key = "HOST_PORT_REMOTE"
-            value = "grpc-test.sandbox.googleapis.com"
-            isEnabled = "YES">
-         </EnvironmentVariable>
          <EnvironmentVariable
             key = "GRPC_CFSTREAM_RUN_LOOP"
             value = "1"
             isEnabled = "YES">
          </EnvironmentVariable>
-         <EnvironmentVariable
-            key = "HOST_PORT_LOCALSSL"
-            value = "localhost:5051"
-            isEnabled = "YES">
-         </EnvironmentVariable>
       </EnvironmentVariables>
    </LaunchAction>
    <ProfileAction

src/objective-c/tests/run_one_test.sh

@@ -79,16 +79,14 @@ fi
 
 XCODEBUILD_FILTER_OUTPUT_SCRIPT="./xcodebuild_filter_output.sh"
 
-export HOST_PORT_LOCALSSL=localhost:$TLS_PORT
-export HOST_PORT_LOCAL=localhost:$PLAIN_PORT
-export HOST_PORT_REMOTE=grpc-test.sandbox.googleapis.com
+TEST_DEFS="HOST_PORT_LOCAL=localhost:$PLAIN_PORT \
+HOST_PORT_LOCALSSL=localhost:$TLS_PORT \
+HOST_PORT_REMOTE=grpc-test.sandbox.googleapis.com \
+GCC_OPTIMIZATION_LEVEL=s"
 
 time xcodebuild \
     -workspace Tests.xcworkspace \
     -scheme $SCHEME \
-    -destination "$DESTINATION" \
-    HOST_PORT_LOCALSSL=$HOST_PORT_LOCALSSL \
-    HOST_PORT_LOCAL=$HOST_PORT_LOCAL \
-    HOST_PORT_REMOTE=$HOST_PORT_REMOTE \
-    GCC_OPTIMIZATION_LEVEL=s \
+    -destination "${DESTINATION}" \
+    GCC_PREPROCESSOR_DEFINITIONS='$GCC_PREPROCESSOR_DEFINITIONS'" $TEST_DEFS" \
     test | "${XCODEBUILD_FILTER_OUTPUT_SCRIPT}"