Support js import statement with ManifestStaticFilesStorage

[blighj]

Browsers now have good support for the import statement of javascript
​https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import#syntax
Which is in the form

import defaultExport from "module-name.js";
import "../module-name2.js";

Something like the below added to the js patterns of HashedFilesMixin should cover both use cases

                (
                    r"""(?P<matched>import(?P<from>[\s\{].*?from)\s*?['"](?P<url>[\w\.\/-]*?)["']\s*?;)""",
                    """import%(from)s"%(url)s";""",
                ),
                (
                    r"""(?P<matched>import\s*?['"](?P<url>[\w\.\/-]*?)["']\s*?;)""",
                    """import"%(url)s";""",
                ),

[Keryn Knight]

Possibly this is a duplicate of #32319, which had an implementation, but had to be reverted due to #33253.

[blighj]

Yes it's a duplicate, closing this ticket.

[Mariusz Felisiak <felisiak.mariusz@…>]

In c179ad9f:

Refs #34100 -- Made file upload tests use Storage.exists() where appropriate.