rename ReactFiberContext to ReactFiberLegacyContext (#33622)

It wasn't immediately obvious to me, that all the exports here are
related to legacy context, so renaming for clarity.

Modern context lives in `ReactFiberNewContext` which we could probably
also raname in a separate step to just Context.

packages/react-reconciler/src/ReactFiberBeginWork.js

@@ -236,7 +236,7 @@ import {
   isContextProvider as isLegacyContextProvider,
   pushTopLevelContextObject,
   invalidateContextProvider,
-} from './ReactFiberContext';
+} from './ReactFiberLegacyContext';
 import {
   getIsHydrating,
   enterHydrationState,

packages/react-reconciler/src/ReactFiberClassComponent.js

@@ -53,7 +53,7 @@ import {
   getUnmaskedContext,
   hasContextChanged,
   emptyContextObject,
-} from './ReactFiberContext';
+} from './ReactFiberLegacyContext';
 import {readContext, checkIfContextChanged} from './ReactFiberNewContext';
 import {requestUpdateLane, scheduleUpdateOnFiber} from './ReactFiberWorkLoop';
 import {
@@ -695,7 +695,7 @@ function constructClassInstance(
   }
 
   // Cache unmasked context so we can avoid recreating masked context unless necessary.
-  // ReactFiberContext usually updates this cache but can't for newly-created instances.
+  // ReactFiberLegacyContext usually updates this cache but can't for newly-created instances.
   if (isLegacyContextConsumer) {
     cacheContext(workInProgress, unmaskedContext, context);
   }

packages/react-reconciler/src/ReactFiberCompleteWork.js

@@ -150,7 +150,7 @@ import {
   isContextProvider as isLegacyContextProvider,
   popContext as popLegacyContext,
   popTopLevelContextObject as popTopLevelLegacyContextObject,
-} from './ReactFiberContext';
+} from './ReactFiberLegacyContext';
 import {popProvider} from './ReactFiberNewContext';
 import {
   prepareToHydrateHostInstance,

packages/react-reconciler/src/ReactFiberHotReloading.js

@@ -20,7 +20,7 @@ import {
 } from './ReactFiberWorkLoop';
 import {enqueueConcurrentRenderForLane} from './ReactFiberConcurrentUpdates';
 import {updateContainerSync} from './ReactFiberReconciler';
-import {emptyContextObject} from './ReactFiberContext';
+import {emptyContextObject} from './ReactFiberLegacyContext';
 import {SyncLane} from './ReactFiberLane';
 import {
   ClassComponent,

packages/react-reconciler/src/ReactFiberReconciler.js

@@ -57,7 +57,7 @@ import {
   processChildContext,
   emptyContextObject,
   isContextProvider as isLegacyContextProvider,
-} from './ReactFiberContext';
+} from './ReactFiberLegacyContext';
 import {createFiberRoot} from './ReactFiberRoot';
 import {isRootDehydrated} from './ReactFiberShellHydration';
 import {

packages/react-reconciler/src/ReactFiberUnwindWork.js

@@ -49,7 +49,7 @@ import {
   isContextProvider as isLegacyContextProvider,
   popContext as popLegacyContext,
   popTopLevelContextObject as popTopLevelLegacyContextObject,
-} from './ReactFiberContext';
+} from './ReactFiberLegacyContext';
 import {popProvider} from './ReactFiberNewContext';
 import {popCacheProvider} from './ReactFiberCacheComponent';
 import {transferActualDuration} from './ReactProfilerTimer';

packages/react-reconciler/src/ReactFiberWorkLoop.js

@@ -357,7 +357,7 @@ import {
   flushSyncWorkOnLegacyRootsOnly,
   requestTransitionLane,
 } from './ReactFiberRootScheduler';
-import {getMaskedContext, getUnmaskedContext} from './ReactFiberContext';
+import {getMaskedContext, getUnmaskedContext} from './ReactFiberLegacyContext';
 import {logUncaughtError} from './ReactFiberErrorLogger';
 import {
   deleteScheduledGesture,