Improve the Server Actions SWC transform (#61001)
This PR improves the Server Actions SWC transform to make it able to
handle nested Action declarations (check
`fixture/server-actions/server/28/input.js` for more details).
It is also a simplification of that transform's internal states and
methods, with the removal of an extra AST pass
(`stmts.visit_mut_with(&mut ClosureActionReplacer {
replaced_action_proxies: &self.replaced_action_proxies, })`). The
generated code is also smaller in some cases. So overall I'd expect the
compilation and runtime performance to improve as well.
## Details
With this change, we're now using `self.declared_idents` and
`self.names` to track closure arguments. `declared_idents` keeps the
identifiers **declared** in the current closure and above. `names` keeps
identifiers **appeared** in the current closure and above. In an example
of the following cursor:
```ts
let x
async function foo() {
"use server"
let y
async function bar() {
"use server"
let z
console.log(x, y, z)
}
// <- cursor
}
```
`declared_idents` would be `y` (`x` isn't in a closure), and `names`
would be `x, y, z`. By manipulating these two states we're able to track
closure closed-up variables recursively.
Closes NEXT-2189
