[DOM] disable legacy mode behind flag (#28468)

Adds a flag to disable legacy mode. Currently this flag is used to cause
legacy mode apis like render and hydrate to throw. This change also
removes render, hydrate, unmountComponentAtNode, and
unstable_renderSubtreeIntoContainer from the experiemntal entrypoint.
Right now for Meta builds this flag is off (legacy mode is still
supported). In OSS builds this flag matches __NEXT_MAJOR__ which means
it currently is on in experiemental. This means that after merging
legacy mode is effectively removed from experimental builds. While this
is a breaking change, experimental builds are not stable and users can
pin to older versions or update their use of react-dom to no longer use
legacy mode APIs.

DiffTrain build for commit 1c02b9d.

Author: gnoff

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react-test-renderer/cjs/ReactTestRenderer-dev.js

@@ -25733,7 +25733,7 @@ if (__DEV__) {
       return root;
     }
 
-    var ReactVersion = "18.3.0-canary-034130c02-20240303";
+    var ReactVersion = "18.3.0-canary-1c02b9d2b-20240304";
 
     // Might add PROFILE later.
 

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react-test-renderer/cjs/ReactTestRenderer-prod.js

@@ -9173,7 +9173,7 @@ var devToolsConfig$jscomp$inline_1014 = {
     throw Error("TestRenderer does not support findFiberByHostInstance()");
   },
   bundleType: 0,
-  version: "18.3.0-canary-034130c02-20240303",
+  version: "18.3.0-canary-1c02b9d2b-20240304",
   rendererPackageName: "react-test-renderer"
 };
 var internals$jscomp$inline_1195 = {
@@ -9204,7 +9204,7 @@ var internals$jscomp$inline_1195 = {
   scheduleRoot: null,
   setRefreshHandler: null,
   getCurrentFiber: null,
-  reconcilerVersion: "18.3.0-canary-034130c02-20240303"
+  reconcilerVersion: "18.3.0-canary-1c02b9d2b-20240304"
 };
 if ("undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__) {
   var hook$jscomp$inline_1196 = __REACT_DEVTOOLS_GLOBAL_HOOK__;

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react-test-renderer/cjs/ReactTestRenderer-profiling.js

@@ -9601,7 +9601,7 @@ var devToolsConfig$jscomp$inline_1056 = {
     throw Error("TestRenderer does not support findFiberByHostInstance()");
   },
   bundleType: 0,
-  version: "18.3.0-canary-034130c02-20240303",
+  version: "18.3.0-canary-1c02b9d2b-20240304",
   rendererPackageName: "react-test-renderer"
 };
 var internals$jscomp$inline_1236 = {
@@ -9632,7 +9632,7 @@ var internals$jscomp$inline_1236 = {
   scheduleRoot: null,
   setRefreshHandler: null,
   getCurrentFiber: null,
-  reconcilerVersion: "18.3.0-canary-034130c02-20240303"
+  reconcilerVersion: "18.3.0-canary-1c02b9d2b-20240304"
 };
 if ("undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__) {
   var hook$jscomp$inline_1237 = __REACT_DEVTOOLS_GLOBAL_HOOK__;

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react/cjs/React-dev.js

@@ -26,7 +26,7 @@ if (__DEV__) {
     }
     var dynamicFlags = require("ReactNativeInternalFeatureFlags");
 
-    var ReactVersion = "18.3.0-canary-034130c02-20240303";
+    var ReactVersion = "18.3.0-canary-1c02b9d2b-20240304";
 
     // ATTENTION
     // When adding new symbols to this file,

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react/cjs/React-prod.js

@@ -598,4 +598,4 @@ exports.useSyncExternalStore = function (
 exports.useTransition = function () {
   return ReactCurrentDispatcher.current.useTransition();
 };
-exports.version = "18.3.0-canary-034130c02-20240303";
+exports.version = "18.3.0-canary-1c02b9d2b-20240304";

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react/cjs/React-profiling.js

@@ -594,7 +594,7 @@ exports.useSyncExternalStore = function (
 exports.useTransition = function () {
   return ReactCurrentDispatcher.current.useTransition();
 };
-exports.version = "18.3.0-canary-034130c02-20240303";
+exports.version = "18.3.0-canary-1c02b9d2b-20240304";
 "undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ &&
   "function" ===
     typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.registerInternalModuleStop &&

compiled-rn/facebook-fbsource/xplat/js/react-native-github/Libraries/Renderer/REVISION

@@ -1 +1 @@
-034130c02ffb47b0026059b57d17e9b080976ff3
+1c02b9d2bdc18091cc6afec810fc1b361f00abdd