clang-format: [JS] Correctly format JavaScript imports with long module paths

Currently the `UnwrappedLineParser` fails to correctly unwrap JavaScript
imports where the module path is not on the same line as the `from` keyword.
For example:

    import {A} from
    'some/path/longer/than/column/limit/module.js';```

This causes issues when in the middle a list of imports because the formatter
thinks it has reached the end of the imports, and therefore will not sort any
imports lower in the list.

The formatter will, however, split the `from` keyword and the module path if
the path exceeds the column limit, which triggers the issue the next time the
file is formatted.

Patch originally by Jared Neil - thanks!

Differential Revision: https://reviews.llvm.org/D34920

llvm-svn: 308306