Remove the lookahead check and just set that a potential arrow function
is there.

Needs to be solo or wrapped in parens. Also update function name to
test in `await` tests so we can use `await f` in the ban test name.

Put least expensive check first.

This can be derived with the following check:

```js
t.isBinaryExpression(node, { operator: "|>" }) &&
  t.isBinaryExpression(node.left, { operator: "|>" })
```

* master: (58 commits)
  Remove dependency on home-or-tmp package (babel#9678)
  [proposal-object-rest-spread] fix templateLiteral in extractNormalizedKeys (babel#9628)
  Partial application plugin (babel#9474)
  Private Static Class Methods (Stage 3) (babel#9446)
  gulp-uglify@3.0.2
  rollup@1.6.0
  eslint@5.15.1
  jest@24.5.0
  regexpu-core@4.5.4
  Remove input and length from state (babel#9646)
  Switch from rollup-stream to rollup and update deps (babel#9640)
  System modules - Hoist classes like other variables (babel#9639)
  fix: Don't transpile ES2018 symbol properties (babel#9650)
  Add WarningsToErrorsPlugin to webpack to avoid missing build problems on CI (babel#9647)
  Update regexpu-core dependency (babel#9642)
  Add placeholders support to @babel/types and @babel/generator (babel#9542)
  Generate plugins file
  Make babel-standalone an ESModule and enable flow (babel#9025)
  Reorganize token types and use a map for them (babel#9645)
  [TS] Allow context type annotation on getters/setters (babel#9641)
  ...

This should resolve the scoping issues we're seeing in the transform.

This also needs to check, when there's a pipeline operator within
the arrow or object, that it parses correctly.

More nested pipeline logic.

This isn't strictly need, as it's just an extra layer of nesting and
provides no additional information.