esbuild 0.12.2

Fix various code generation and minification issues (#1305)

This release fixes the following issues, which were all identified by running esbuild against the latest UglifyJS test suite:
- The in operator is now surrounded parentheses inside arrow function expression bodies inside for loop initializers:
```
// Original code
for ((x => y in z); 0; ) ;

// Old output
for ((x) => y in z; 0; ) ;

// New output
for ((x) => (y in z); 0; ) ;
```
  Without this, the in operator would cause the for loop to be considered a for-in loop instead.
- The statement return undefined; is no longer minified to return; inside async generator functions:
```
// Original code
return undefined;

// Old output
return;

// New output
return void 0;
```
  Using return undefined; inside an async generator function has the same effect as return await undefined; which schedules a task in the event loop and runs code in a different order than just return;, which doesn't hide an implicit await expression.
- Property access expressions are no longer inlined in template tag position:
```
// Original code
(null, a.b)``, (null, a[b])``;

// Old output
a.b``, a[b]``;

// New output
(0, a.b)``, (0, a[b])``;
```
  The expression a.b`c` is different than the expression (0, a.b)`c`. The first calls the function a.b with a as the value for this but the second calls the function a.b with the default value for this (the global object in non-strict mode or undefined in strict mode).
- Verbatim __proto__ properties inside object spread are no longer inlined when minifying:
```
// Original code
x = { ...{ __proto__: { y: true } } }.y;

// Old output
x = { __proto__: { y: !0 } }.y;

// New output
x = { ...{ __proto__: { y: !0 } } }.y;
```
  A verbatim (i.e. non-computed non-method) property called __proto__ inside an object literal actually sets the prototype of the surrounding object literal. It does not add an "own property" called __proto__ to that object literal, so inlining it into the parent object literal would be incorrect. The presence of a __proto__ property now stops esbuild from applying the object spread inlining optimization when minifying.
- The value of this has now been fixed for lowered private class members that are used as template tags:
```
// Original code
x = (new (class {
  a = this.#c``;
  b = 1;
  #c() { return this }
})).a.b;

// Old output
var _c, c_fn, _a;
x = new (_a = class {
  constructor() {
    __privateAdd(this, _c);
    __publicField(this, "a", __privateMethod(this, _c, c_fn)``);
    __publicField(this, "b", 1);
  }
}, _c = new WeakSet(), c_fn = function() {
  return this;
}, _a)().a.b;

// New output
var _c, c_fn, _a;
x = new (_a = class {
  constructor() {
    __privateAdd(this, _c);
    __publicField(this, "a", __privateMethod(this, _c, c_fn).bind(this)``);
    __publicField(this, "b", 1);
  }
}, _c = new WeakSet(), c_fn = function() {
  return this;
}, _a)().a.b;
```
  The value of this here should be an instance of the class because the template tag is a property access expression. However, it was previously the default value (the global object in non-strict mode or undefined in strict mode) instead due to the private member transformation, which is incorrect.
- Invalid escape sequences are now allowed in tagged template literals
  
  This implements the template literal revision feature: https://github.com/tc39/proposal-template-literal-revision. It allows you to process tagged template literals using custom semantics that don't follow JavaScript escape sequence rules without causing a syntax error:
```
console.log((x => x.raw)`invalid \unicode escape sequence`)
```