chore: improve code generation for bind:this in SSR mode

[Rich-Harris]

We do the whole $$settled dance in SSR for components with bind:this, quite unnecessarily. Given this input...

<Child bind:this={child} />

...this PR produces much better output:

// old
export default function App($$payload, $$props) {
  $.push(false);

  let $$settled = true;
  let $$inner_payload;

  function $$render_inner($$payload) {
    const anchor = $.create_anchor($$payload);

    $$payload.out += `${anchor}`;

    Foo($$payload, {
      get this() {
        return foo;
      },
      set this($$value) {
        foo = $$value;
        $$settled = false;
      }
    });

    $$payload.out += `${anchor}`;
  };

  do {
    $$settled = true;
    $$inner_payload = $.copy_payload($$payload);
    $$render_inner($$inner_payload);
  } while (!$$settled);

  $.assign_payload($$payload, $$inner_payload);
  $.pop();
}

// new
export default function App($$payload, $$props) {
  $.push(false);

  const anchor = $.create_anchor($$payload);

  $$payload.out += `${anchor}`;
  Foo($$payload, {});
  $$payload.out += `${anchor}`;
  $.pop();
}

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• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

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• Run the tests with pnpm test and lint the project with pnpm lint

[changeset-bot]

🦋 Changeset detected

Latest commit: 321db79

The changes in this PR will be included in the next version bump.

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