minifier: does not eliminate unnecessary side-effect free function call

[TheAlexLichter]

Case

When a side-effect free function is called multiple times, the call could be removed. Same applies to unused variables assigned to the result of the side-effect free function

Reproduction

Expected output

function foo() {
  return !0
}

const a = foo();

console.log(a);

or a smaller version like - though above would suffice for now.

```ts
function foo() {
  return !0
}

console.log(foo());

Actual output

function foo() {
	return !0;
}
const a = foo();
foo(), foo(), console.log(a);

Info

Originally reported in rolldown/rolldown#5712

[TheAlexLichter]

Resolved via #13026

[sapphi-red]

The linked repro was not fixed. foo() is still included in the output.

I guess

function foo() {
  return !0
}

needs to be marked as side effect free, but IIRC Oxc currently only marks functions that is empty as side effect free.

[sapphi-red]

Fixed by #13403