[Bug]: Babel does not transpile Unicode identifier names for early engine targets

### 💻

- [ ] Would you like to work on a fix?

### How are you using Babel?

@babel/cli

### Input code

```js
let ℮;
```
Here is the [REPL](https://babel.dev/repl#?browsers=defaults%2C%20not%20ie%2011%2C%20not%20ie_mob%2011&build=&builtIns=false&corejs=false&spec=true&loose=true&code_lz=DYUwLgBIdIQNxA&debug=false&forceAllTransforms=true&shippedProposals=true&circleciRepo=&evaluate=true&fileSize=true&timeTravel=false&sourceType=unambiguous&lineWrap=false&presets=env&prettier=false&targets=Node-10.13&version=7.18.12&externalPlugins=&assumptions=%7B%7D)

### Configuration file name

babel.config.json

### Configuration

```json
{
"sourceType": "unambiguous",
"presets": ["@babel/preset-env"],
"plugins": [
"@babel/plugin-transform-runtime"
]
}
```
### Current and expected behavior

'Unicode 8' is only available in ES6, but babel doesn't transpile unicode 8.

### Environment

- babel
- - ├── @babel/cli@7.18.12
- - ├── @babel/plugin-transform-runtime@7.18.12
- - ├── @babel/preset-env@7.18.12
- Node: [v17.3.0]
- npm version [8.5.2]
- os [ubuntu 20.04]

### Possible solution

_No response_

### Additional context

_No response_

Start with the provided @babel/cli reproduction using @babel/preset-env, the input `let ℮;`, and the Node 10.13 target. Check how Babel handles Unicode 8 identifiers for early engine targets and compare the generated output with the expected compatible form. Done means the reproduction no longer leaves the Unicode identifier untranspiled.

Written by the indexing model from the issue text.