Remove Babylon plugins for features already merged to the ECMAScript spec (#8448)

These are now enabled by default:
- objectRestSpread (2018)
- asyncGenerators (2018)
- optionalCatchBInding (2019)
- jsonStrings (2019)

TODO (after this commit):
- [ ] Deprecate the `@babel/plugin-syntax-*` packages.
- [ ] Deprecate the `@babel/plugin-proposal-*` packages.
- [ ] Create the `@babel/plugin-transform-*` packages.

packages/babel-parser/test/fixtures/es2015/arrow-functions/object-rest-spread/options.json

@@ -1,3 +0,0 @@
-{
-  "plugins": ["objectRestSpread"]
-}

packages/babel-parser/test/fixtures/experimental/_no-plugin/async-generators/input.js

@@ -1 +0,0 @@
-async function * f () {}

packages/babel-parser/test/fixtures/experimental/_no-plugin/async-generators/options.json

@@ -1,4 +0,0 @@
-{
-  "throws": "This experimental syntax requires enabling the parser plugin: 'asyncGenerators' (1:15)",
-  "plugins": []
-}

packages/babel-parser/test/fixtures/experimental/_no-plugin/object-rest-spread/input.js

@@ -1 +0,0 @@
-({...x})

packages/babel-parser/test/fixtures/experimental/_no-plugin/object-rest-spread/options.json

@@ -1,4 +0,0 @@
-{
-  "throws": "This experimental syntax requires enabling the parser plugin: 'objectRestSpread' (1:2)",
-  "plugins": []
-}

packages/babel-parser/test/fixtures/experimental/async-generators/options.json

@@ -1,3 +0,0 @@
-{
-  "plugins": ["asyncGenerators"]
-}

packages/babel-parser/test/fixtures/experimental/class-private-methods/async-generator/options.json

@@ -1,3 +1,3 @@
 {
-  "plugins": ["classPrivateMethods", "asyncGenerators"]
+  "plugins": ["classPrivateMethods"]
 }

packages/babel-parser/test/fixtures/experimental/json-strings/options.json

@@ -1,3 +0,0 @@
-{
-  "plugins": ["jsonStrings"]
-}

packages/babel-parser/test/fixtures/experimental/object-rest-spread/options.json

@@ -1,3 +0,0 @@
-{
-  "plugins": ["objectRestSpread"]
-}

packages/babel-parser/test/fixtures/experimental/optional-catch-binding/no-plugin-no-binding-finally/options.json

@@ -1,3 +0,0 @@
-{
-  "throws": "This experimental syntax requires enabling the parser plugin: 'optionalCatchBinding' (4:6)"
-}

packages/babel-parser/test/fixtures/experimental/optional-catch-binding/no-plugin-no-binding/options.json

@@ -1,3 +0,0 @@
-{
-  "throws": "This experimental syntax requires enabling the parser plugin: 'optionalCatchBinding' (4:6)"
-}

packages/babel-parser/test/fixtures/experimental/optional-catch-binding/no-plugin-yes-binding-finally/input.js

@@ -1,4 +0,0 @@
-try {
-} catch (err) {
-} finally {
-}

packages/babel-parser/test/fixtures/experimental/optional-catch-binding/no-plugin-yes-binding-finally/output.json

@@ -1,134 +0,0 @@
-{
-  "type": "File",
-  "start": 0,
-  "end": 35,
-  "loc": {
-    "start": {
-      "line": 1,
-      "column": 0
-    },
-    "end": {
-      "line": 4,
-      "column": 1
-    }
-  },
-  "program": {
-    "type": "Program",
-    "start": 0,
-    "end": 35,
-    "loc": {
-      "start": {
-        "line": 1,
-        "column": 0
-      },
-      "end": {
-        "line": 4,
-        "column": 1
-      }
-    },
-    "sourceType": "script",
-    "interpreter": null,
-    "body": [
-      {
-        "type": "TryStatement",
-        "start": 0,
-        "end": 35,
-        "loc": {
-          "start": {
-            "line": 1,
-            "column": 0
-          },
-          "end": {
-            "line": 4,
-            "column": 1
-          }
-        },
-        "block": {
-          "type": "BlockStatement",
-          "start": 4,
-          "end": 7,
-          "loc": {
-            "start": {
-              "line": 1,
-              "column": 4
-            },
-            "end": {
-              "line": 2,
-              "column": 1
-            }
-          },
-          "body": [],
-          "directives": []
-        },
-        "handler": {
-          "type": "CatchClause",
-          "start": 8,
-          "end": 23,
-          "loc": {
-            "start": {
-              "line": 2,
-              "column": 2
-            },
-            "end": {
-              "line": 3,
-              "column": 1
-            }
-          },
-          "param": {
-            "type": "Identifier",
-            "start": 15,
-            "end": 18,
-            "loc": {
-              "start": {
-                "line": 2,
-                "column": 9
-              },
-              "end": {
-                "line": 2,
-                "column": 12
-              },
-              "identifierName": "err"
-            },
-            "name": "err"
-          },
-          "body": {
-            "type": "BlockStatement",
-            "start": 20,
-            "end": 23,
-            "loc": {
-              "start": {
-                "line": 2,
-                "column": 14
-              },
-              "end": {
-                "line": 3,
-                "column": 1
-              }
-            },
-            "body": [],
-            "directives": []
-          }
-        },
-        "guardedHandlers": [],
-        "finalizer": {
-          "type": "BlockStatement",
-          "start": 32,
-          "end": 35,
-          "loc": {
-            "start": {
-              "line": 3,
-              "column": 10
-            },
-            "end": {
-              "line": 4,
-              "column": 1
-            }
-          },
-          "body": [],
-          "directives": []
-        }
-      }
-    ],
-    "directives": []
-  }
-}

packages/babel-parser/test/fixtures/experimental/optional-catch-binding/no-plugin-yes-binding/input.js

@@ -1,2 +0,0 @@
-try {
-} catch (err) {}