[Nala]: Temporarily override TonalOutline in dark mode

[fallaciousreasoning]

Resolves brave/brave-browser#41125

Note: This doesn't fix the devtools Clear storage button issue @AlanBreck found - I need to patch devtools for that so I'm going to do that in a separate PR

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:

[fallaciousreasoning]

This should probably be uplifted to 1.71

[MadhaviSeelam]

Verification PASSED using

Brave | 1.72.35 Chromium: 129.0.6668.59 (Official Build) nightly (64-bit)
-- | --
Revision | 8cd08e988791e9af165a231677472ffaaa5ae548
OS | Windows 11 Version 23H2 (Build 22631.4169)

Verified using STR from brave/brave-browser#41125 (comment)

Confirmed using dark theme, some of the buttons no longer show an orange ring/outline.

Verified buttons don't show orange/outline in light theme as expected.

dark	light