TypeScript: `import x = A.x` syntax should always be converted to a var declaration

Example input code:

```ts
namespace A {
export var x = 0;
}
import x = A.x;
console.log(x);
```

TypeScript 6.0.2 with `"target": "ES2020"` ([playground](https://www.typescriptlang.org/play/?target=7&module=1&ts=6.0.2#code/HYQwtgpgzgDiDGEAEBBJBvAUEnSIA8YB7AJwBckA3EEpfJAXiQAYBuTAX0wEsxjy6jVADp87eEWBQiAGwjCZRAOYAKfAEp2QA)):

```js
"use strict";
var A;
(function (A) {
A.x = 0;
})(A || (A = {}));
var x = A.x;
console.log(x);
```

esbuild 0.28.0 with `--target=es2020` ([playground](https://esbuild.github.io/try/#dAAwLjI4LjAALS1sb2FkZXI9dHMgLS10YXJnZXQ9ZXMyMDIwAG5hbWVzcGFjZSBBIHsKICAgIGV4cG9ydCB2YXIgeCA9IDA7Cn0KaW1wb3J0IHggPSBBLng7CmNvbnNvbGUubG9nKHgpOw)):

```js
var A;
((A2) => {
A2.x = 0;
})(A || (A = {}));
const x = A.x;
console.log(x);
```

Start with the TypeScript reproduction from the issue and compare esbuild's output with TypeScript's output for the namespace and import-assignment case. Trace the TypeScript lowering path for `import x = A.x`, then add a regression test showing that this syntax is emitted as a `var` declaration and that the test output matches the intended behavior.

Written by the indexing model from the issue text.