Expose Rewards verbose logging flag on Android

[zenparsing]

Resolves brave/brave-browser#15924

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
• 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:

[mkarolin]

++

[deeppandya]

LGTM

[kjozwiak]

Cases from https://github.com/brave/brave-core/pull/8598

Verification PASSED on Samsung S10+ running Android 11 using the following build:

1.27.10 Chromium: 91.0.4472.70

Error logging

• disconnected the internet/network and attempted to create a wallet within a new profile
• after ~1minute, enabled the network/internet and created a wallet
• connected to a production uphold account
• verified that only errors are appearing in brave://rewards-internals while #brave-rewards-verbose-logging is disabled
• ensured that Refresh, Clear & Download are working as expected

Verbose logging

• enabled #brave-rewards-verbose-logging via brave://flags
• once enabled, created a new wallet
• connected to my production Uphold account
• verified there's more detailed logs present under brave://rewards-internals
• ensured that Refresh, Clear & Download are working as expected

Example	Example	Example

Cases from https://github.com/brave/brave-core/pull/8767

Verification PASSED on Samsung S10+ running Android 11 using the following build:

1.27.10 Chromium: 91.0.4472.70

• verified the STR outlined via Do not log request details for rewards external wallet session endpoints #8767 (comment)
• ensured that clicking on Refresh correctly populates the empty text field with the log
• ensured that clicking on Download log correctly initiates the download process/flow
• ensured that *.uphold.com/oauth2/token didn't appear anywhere within the log after connecting to an Uphold account
  • also searched for oauth2 & oauth2/token within the log as a double check