Dynamic method names prevent tree shaking

Using dynamic class method names prevents the class to be discarded by tree shaking when it is not used.

Example:

```js
// input.js

const method = 'name';

class A {
greet() {
console.log('hello from A');
}

[method]() {
return 'A';
}
}

class B {
greet() {
console.log('hello from B');
}
}

new B().greet();
```

I have tried to add various `/* @__PURE__ */` annotations, but the class A does not get tree shaken.
The above example is deliberately simple to demonstrate the issue, but the context where it came from is that any class that declares a custom inspect function like below prevents treeshaking:

```js
[Symbol.for('nodejs.util.inspect.custom')]() {
return '...';
}
```

Here is a link to the playground to reproduce the issue.
https://esbuild.github.io/try/#dAAwLjE5LjExAC0tdHJlZS1zaGFraW5nPXRydWUAY29uc3QgbWV0aG9kID0gJ21ldGhvZCc7CgpjbGFzcyBBIHsKICBncmVldCgpIHsKICAgIGNvbnNvbGUubG9nKCdoZWxsbyBmcm9tIEEnKTsKICB9CiAgCiAgW21ldGhvZF0oKSB7CiAgICByZXR1cm4gJ0EnOwogIH0KfQoKY2xhc3MgQiB7CiAgZ3JlZXQoKSB7CiAgICBjb25zb2xlLmxvZygnaGVsbG8gZnJvbSBCJyk7CiAgfQp9CgpuZXcgQigpLmdyZWV0KCk7

Start with the linked esbuild playground and the provided input.js reproduction, then inspect tree-shaking behavior for computed class method names. Done means the unused class A is discarded while used class B remains, and the custom inspect example no longer prevents tree shaking.

Written by the indexing model from the issue text.