Add notifications to imports

[spylogsster]

Description

Created from @bbondy comment brave/brave-core#8422 (comment)

Right clicking on a YouTube video (you need to right click twice because youtube tries to override the context menu), allows you to select import Video. But then it gives an error.

IPFS Companion also gives an error.
The error seems OK, but the way we deal with the error is that we don't do anything. IPFS companion does a notification like this for the error. We could do something similar unless you have a better suggestion.

Actual result:

• Nothing happens

Expected result:

• Show notification about import error

Reproduces how often:

easy

Brave version (brave://version info)

Version/Channel Information:

• Can you reproduce this issue with the current release?
• Can you reproduce this issue with the beta channel?
• Can you reproduce this issue with the nightly channel?

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information:

[lidel]

I wrote some details about import failing on some websites in ipfs/ipfs-companion#227 (mostly Firefox, but I feel a variant applies here too).

TLDR: In IPFS Companion it fails due to tracking protection (either regular CORS and other headers set by website, or browser itself behaving more strict for some reason, like in Firefox with protection enabled).

We can't do much in a browser extension, but Brave should be able to side-steps those protections if the request was triggered by user interaction with native Import UI.

[spylogsster]

[stephendonner]

Verified PASSED using the testplan from brave/brave-core#8422 with build

Brave	1.25.28 Chromium: 90.0.4430.72 (Official Build) nightly (x86_64)
Revision	b6172ef8d07ef486489a4b11b66b2eaeed50d132-refs/branch-heads/4430@{#1233}
OS	macOS Version 11.2.3 (Build 20D91)

Steps:

(YouTube video) - import failure

1. loaded https://www.youtube.com/watch?v=_28sorQWw_E&t=22s
2. right-clicked on the video (twice)
3. chose Import to IPFS > Selected video
4. got the import-error message notification below

(MP4 video) - import success

1. loaded https://www.learningcontainer.com/mp4-sample-video-files-download/
2. right-clicked on the 1st video
3. chose Import to IPFS > Selected video
4. got the IPFS Import Completed message notification below
5. confirmed I was able to share the video via link: https://bafybeics24zwxekzwol2brpsubz6es6awjn2eolvpa3jlafqgt4qxvbm3q.ipfs.dweb.link/?filename=sample-mp4-file.mp4

(HTML page) - import partly complete

1. loaded http://en.wikipedia-on-ipfs.org.ipns.localhost:48081/wiki/
2. right-clicked on the page
3. chose Import to IPFS > This page
4. got the import-success message
5. again, right-clicked on the page
6. chose Import to IPFS > This page
7. confirmed I got the IPFS import partly completed message notification

example	example	example

[stephendonner]

@spylogsster @lidel do either of you happen to have a handy use-case for IPFS import partly completed? Thanks!

[spylogsster]

@stephendonner try to import same link twice, next imports will be partially completed because same link already exists in target directory