[compiler] Avoid failing builds when import specifiers conflict or shadow vars (#32663)

Avoid failing builds when imported function specifiers conflict by using
babel's `generateUid`. Failing a build is very disruptive, as it usually
presents to developers similar to a javascript parse error.
```js
import {logRender as _logRender} from 'instrument-runtime';

const logRender = () => { /* local conflicting implementation */ }

function Component_optimized() {
  _logRender(); // inserted by compiler
}
```

Currently, we fail builds (even in `panicThreshold:none` cases) when
import specifiers are detected to conflict with existing local
variables. The reason we destructively throw (instead of bailing out) is
because (1) we first generate identifier references to the conflicting
name in compiled functions, (2) replaced original functions with
compiled functions, and then (3) finally check for conflicts.

When we finally check for conflicts, it's too late to bail out.
```js
// import {logRender} from 'instrument-runtime';

const logRender = () => { /* local conflicting implementation */ }

function Component_optimized() {
  logRender(); // inserted by compiler
}
```