Restore 'import' in default Package Exports conditions (#36902)

Summary:
X-link: facebook/react-native#36902

Reverts facebook/react-native#36584.

Since we've come across example packages (typically targeting Node.js) which only distribute ESM, we believe it's more helpful to return to asserting the `"import"` condition by default, for maximum compatibility. The above issue and comments outline the pros/cons.

Changelog:
[General][Changed] - Default condition set for experimental Package Exports is now ['require', 'import', 'react-native']

Metro changelog: [Experimental] Package Exports unstable_conditionNames now defaults to ['require', 'import']

Reviewed By: robhogan

Differential Revision: D44962143

fbshipit-source-id: 004172388916c902469b49cfc920ebe13c62c430

packages/metro-config/src/__tests__/__snapshots__/loadConfig-test.js.snap

@@ -75,6 +75,7 @@ Object {
     ],
     "unstable_conditionNames": Array [
       "require",
+      "import",
     ],
     "unstable_conditionsByPlatform": Object {
       "web": Array [
@@ -252,6 +253,7 @@ Object {
     ],
     "unstable_conditionNames": Array [
       "require",
+      "import",
     ],
     "unstable_conditionsByPlatform": Object {
       "web": Array [
@@ -429,6 +431,7 @@ Object {
     ],
     "unstable_conditionNames": Array [
       "require",
+      "import",
     ],
     "unstable_conditionsByPlatform": Object {
       "web": Array [
@@ -606,6 +609,7 @@ Object {
     ],
     "unstable_conditionNames": Array [
       "require",
+      "import",
     ],
     "unstable_conditionsByPlatform": Object {
       "web": Array [

packages/metro-config/src/defaults/index.js

@@ -49,7 +49,7 @@ const getDefaultValues = (projectRoot: ?string): ConfigT => ({
     nodeModulesPaths: [],
     resolveRequest: null,
     resolverMainFields: ['browser', 'main'],
-    unstable_conditionNames: ['require'],
+    unstable_conditionNames: ['require', 'import'],
     unstable_conditionsByPlatform: {
       web: ['browser'],
     },