Private class methods stage 3 (#8654)

* Add private method syntax support

* Add private method spec support

* Add private method loose support

* Throw error if static private method is used

* Add more isStatic & isMethod checks

* Remove `writable:false` from private method inits

`writable` is false by default.

* Add private method func obj equality check

* Throw if private accessor is used

* Add check for fields === private method loose mode

* Throw buildCodeFrameErrors instead of Errors

* Move obj destructuring inside for loop

* Remove "computed" from ClassPrivateMethod type def

packages/babel-plugin-proposal-private-methods/test/fixtures/private-method/assignment/input.js

@@ -0,0 +1,9 @@
+class Foo {
+  constructor() {
+    this.publicField = this.#privateMethod();
+  }
+
+  #privateMethod() {
+    return 42;
+  }
+}