Function expressions in a property assignment of a prototype object should be methods, not nested classes

/** @class */
module.exports.C = function() {
  this.x = 1
}
module.exports.C.prototype = {
  m1() {
    this.a = 1
  },
  m2: function() {
    this.b = 2
  }
}
var c = new module.exports.C()
c.a
c.b

Expected behavior:
c.a and c.b both work.

Actual behavior:
Only c.a works; c.b says that 'd' does not exist on type 'C'. There's also an error on this.b = 2 when noImplicitThis: true.

bindThisPropertyAssignment needs to understand that function expressions might be part of a property assignment in an object literal. The code to handle this will probably look like this:

                    // For `{ x: function() }` should modify the object literal's members, not behave like a fresh class (as long as it doesn't have @class on it)
                    if (isPropertyAssignment(thisContainer.parent)) {
                        // wow I hope those parent pointers are set!
                        const containingClass = thisContainer.parent.parent;
                        const symbolTable = containingClass.symbol.members!;
                        if (hasDynamicName(node)) {
                            bindDynamicallyNamedThisPropertyAssignment(node, containingClass.symbol);
                        }
                        else {
                            declareSymbol(symbolTable, containingClass.symbol, node, SymbolFlags.Property | SymbolFlags.Assignment, SymbolFlags.None, /*isReplaceableByMethod*/ true);
                        }
                        break;
                    }

I expect this to break a lot of tests, but it didn't. However, I haven't tried it on the user tests yet.

从 issue 中的复现开始，检查 bindThisPropertyAssignment，尤其要关注 prototype 对象属性赋值中的函数表达式是如何处理的。在 noImplicitThis 下使用所示示例验证行为，包括 c.a 和 c.b 是否都能正常工作，以及报告的诊断是否已消失。