fix(privacy): Generic cosmetic filter list rules are not applied on some sites on iOS

[StephenHeaps]

• An invalid id value was being passed from javascript to Swift to check against the AdblockEngine to determine if it should be hidden. This invalid id was causing the message to fail and never be sent to Swift / native, so it was never checked against the AdblockEngine.
• Fixed by fetching the id via getAttribute, and added a safety string check.

Resolves brave/brave-browser#42471

Submitter Checklist:

• I confirm that no security/privacy review is needed and no other type of reviews are needed, or that I have requested them
• 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 wiki
  • npm run presubmit wiki, 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/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

1. Add custom filter rules:

##.cc-bottom.cc-floating.cc-window
##div.cc-revoke

2. Visit https://laurentferrier.ch/products/classic-auto-sandstone?variant=44866903605410
3. Verify cookie banner is hidden
4. Visit https://www.chefs-edge.com/collections/whetstones/products/shapton-rockstar-whetstone-1000-grit
5. Verify cookie banner is hidden
6. Visit https://goldammer.me/collections/all
7. Verify cookie banner is hidden

[brave-builds]

Released in v1.75.50

[kjozwiak]

Verification PASSED on iPhone 11 running iOS 18.1 using the following build(s):

Brave | 1.75.50 Chromium: 131.0.6778.85 (Official Build) nightly (64-bit)
--- | ---
Revision | 51f4782c9391...
OS | iOS

Using the STR/Cases outlined via #26729 (comment), ensured that the cookie banners are not appearing on the websites mentioned above as per the following:

https://laurentferrier.ch/products/classic-auto-sandstone?variant=44866903605410

ScreenRecording_11-26-2024.16-06-26_1.MP4

https://www.chefs-edge.com/collections/whetstones/products/shapton-rockstar-whetstone-1000-grit

ScreenRecording_11-26-2024.16-07-44_1.MP4

https://goldammer.me/collections/all

ScreenRecording_11-26-2024.16-08-47_1.MP4