Android-components: Improve our download manger to be able to forward downloads to external download manager

[Amejia481]

Before performing a download we have to verify if there are other apps that download this file.

If so:
Create a custom intent chooser(https://github.com/mozilla-mobile/android-components/issues/4770#issuecomment-543777062) and includes the actual app on the list. If the user selects the app from the dialog immediately download the file.

Otherwise:
Download the file without showing an dialog chooser.

See this comment for reference about how Fennec handles this.

This feature should be configurable, the app able will be able to indicate this behavior should be applied or if the download should be download immediately.

[andreicristianpetcu]

Should this work with Download Navi? I can't get it to work.

[cadeyrn]

@andreicristianpetcu How did you test? Did you try in Fenix? There hasn't been an AC update in Fenix since that AC change landed.

[andreicristianpetcu]

I tried in Fenix. I'll look at ac updates next time

[Amejia481]

Should this work with Download Navi? I can't get it to work.

I should work with any third party app, as long as they are handling downloads intents correctly :)

[Amejia481]

The feature will be available after this pr lands