Fixed shields v2 crash with multiple windows

[simonhong]

fix brave/brave-browser#22224
fix brave/brave-browser#21575
fix brave/brave-browser#22031
fix brave/brave-browser#21934

ShieldsPanelDataHandler should keep observed data controller
instead of getting data controller from active web contents of current
active window because active window could be different on it's created
or destroyed.
Crash happened because ShieldsPanelDataHandler tried to remove itself
from wrong data controller due to above reason.

Resolves

Submitter Checklist:

• I confirm that no security/privacy review is needed, or that I have requested one
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally: npm run test -- brave_browser_tests, npm run test -- brave_unit_tests, npm run lint, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Custom-Headers
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

See the linked issue

[nullhook]

this issue seems related: brave/brave-browser#22275

[nullhook]

lgtm - other than the comment change

[stephendonner]

Verified PASSED using

Brave	1.39.61 Chromium: 100.0.4896.88 (Official Build) nightly (x86_64)
Revision	4450653bfa91182e85723d8f1dee64dd6ce40ed4-refs/branch-heads/4896@{#1086}
OS	macOS Version 12.4 (Build 21F5048e)

Confirmed no more/new crashes when following my original steps + exploratory testing, too.

[stephendonner]

Verified PASSED using

Brave	1.39.68 Chromium: 101.0.4951.34 (Official Build) nightly (x86_64)
Revision	8f93af5d759634c5256b65997dedd138ed60992f-refs/branch-heads/4951@{#710}
OS	macOS Version 12.4 (Build 21F5048e)

Checked:

• Crash in BraveShieldsDataController::OnFaviconUpdated when toggling Brave Shields status between two same-site windows brave-browser#22224 using twitch.tv (two or more windows), toggling Brave Shields on/off
• Crashing in BraveShieldsDataController::ClearAllResourcesList() toggling Block scripts brave-browser#21575 using aol.com/news (two or more windows), toggling Brave Shields on/off
• Crash in BraveShieldsDataController::HandleItemBlocked brave-browser#22031 using cnn.com and youtube.com, toggling Brave Shields on/off
• Crash on Mac Nightly brave-browser#21934 using https://d3ward.github.io/toolz/adblock.html, toggling Brave Shields on/off, changing options