Multiple imports in one statement (like variable declarations)

As discussed in other issues, imports can be relatively verbose. So instead of forcing programmers to type `import` every time they want to import something, why not be able to chain imports into one statement?
From
```dart
import "dart:math" as math;
import "dart:async";
import "package:flutter/material.dart";
import "util.dart";
```
to
```dart
import "dart:math" as math, "dart:async", "package:flutter/material.dart", "util.dart";
```
or
```dart
import ["dart:math" as math, "dart:async", "package:flutter/material.dart", "util.dart"];
```
or
```dart
import (
"dart:math" as math,
"dart:async",
"package:flutter/material.dart",
"util.dart"
);
```
To remove ambiguity, maybe imports using `show` or `hide` couldn't be chained in this manner.

Review the proposed chained and parenthesized import syntaxes, including the restriction suggested for imports using show or hide. Determine whether the language design should support this feature and which syntax and ambiguity rules would be acceptable.

Written by the indexing model from the issue text.