Use brave theme type as a system dark mode on Windows

[simonhong]

Aligning base UI theme(ex, context menu) with brave theme was not
implemented on Windows because Windows doesn't support per-application
theme. Whereas, MacOS support it. So, when user set dark or light, it is
set as a application theme.
To solve this on Windows, NativeThemeWin::SystemDarkModeEnabled() checks
whether dark mode enabling is overridden or not.
Overridden value is set by client(BraveThemeService).

Fix brave/brave-browser#4056
Fix brave/brave-browser#4272
Fix brave/brave-browser#3804

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Verified that these changes build without errors on
  • Windows
  • macOS
  • Linux
• Verified that these changes pass automated tests (npm test brave_unit_tests && npm test brave_browser_tests && npm run test-security) on
  • Windows
  • macOS
  • Linux
• Verified that all lint errors/warnings are resolved (npm run lint)
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Yes or QA/No) to include the closed issue in milestone
• Public documentation has been updated as necessary. 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-Protection-Mode
  • 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-issues-with-tracking-protection

Test Plan:

1. Start browser on Win10 and open settings page
2. Set brave theme to light or dark
3. Change os theme to dark or light and check settings page theme is not changed.
4. Set brave theme to Same as Windows
5. Change os theme to dark or light and check settings page theme is changed

Other manual tests are described in related issues.

yarn test brave_browser_tests --filter=BraveThemeServiceTest.SystemThemeChangeTest

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

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.

[simonhong]

security test is failed on Builder.

[simonhong]

Kindly ping..

[petemill]

Works really nicely 🎨

[petemill]

Before merging, re-running PR builder due to previous time-out failure...

PR builder not passed yet

[simonhong]

@petemill Yup, will rebase again! thanks for review

[petemill]

@simonhong most recent failure is possibly:

19:07:52  
19:07:52  python C:\jenkins\workspace\eme_with_native_theme_on_windows\scripts\lint.py --project_root=C:\jenkins\workspace\eme_with_native_theme_on_windows\src --base_branch=origin/master
19:07:54  Done processing browser\themes\brave_theme_service.cc
19:07:54  
19:07:54  browser\themes\brave_theme_service.h:6:  #ifndef header guard has wrong style, please use: JENKINS_WORKSPACE_EME_WITH_NATIVE_THEME_ON_WINDOWS_SRC_BRAVE_BROWSER_THEMES_BRAVE_THEME_SERVICE_H_  
19:07:54  [build/header_guard] [5]
19:07:54  
19:07:54  browser\themes\brave_theme_service.h:88:  #endif line should be "#endif  // JENKINS_WORKSPACE_EME_WITH_NATIVE_THEME_ON_WINDOWS_SRC_BRAVE_BROWSER_THEMES_BRAVE_THEME_SERVICE_H_"  
19:07:54  [build/header_guard] [5]
19:07:54  

[simonhong]

@simonhong most recent failure is possibly:

19:07:52  
19:07:52  python C:\jenkins\workspace\eme_with_native_theme_on_windows\scripts\lint.py --project_root=C:\jenkins\workspace\eme_with_native_theme_on_windows\src --base_branch=origin/master
19:07:54  Done processing browser\themes\brave_theme_service.cc
19:07:54  
19:07:54  browser\themes\brave_theme_service.h:6:  #ifndef header guard has wrong style, please use: JENKINS_WORKSPACE_EME_WITH_NATIVE_THEME_ON_WINDOWS_SRC_BRAVE_BROWSER_THEMES_BRAVE_THEME_SERVICE_H_  
19:07:54  [build/header_guard] [5]
19:07:54  
19:07:54  browser\themes\brave_theme_service.h:88:  #endif line should be "#endif  // JENKINS_WORKSPACE_EME_WITH_NATIVE_THEME_ON_WINDOWS_SRC_BRAVE_BROWSER_THEMES_BRAVE_THEME_SERVICE_H_"  
19:07:54  [build/header_guard] [5]
19:07:54  

@petemill Hmm, no lint error on local.. Lint gave invalid suggestion. seems lint bug..

[petemill]

Exciting!