Fixes Brave Ads crash when parsing country code from subdivision targeting code

[tmancey]

Resolves brave/brave-browser#12030

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
  • Android
  • iOS
  • Linux
  • macOS
  • Windows
• Verified that these changes pass automated tests (unit, browser, security tests) on
  • iOS
  • Linux
  • macOS
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• Verified that all lint errors/warnings are resolved (npm run lint, npm run gn_check)
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Requested a security/privacy review as needed.
• Added appropriate QA labels (QA/Yes or QA/No) to the associated issue
• Added appropriate release note labels (release-notes/include or release-notes/exclude) to the associated issue
• 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-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-issues-with-tracking-protection
  • https://github.com/brave/brave-browser/wiki/QA-Guide

Test Plan:

• Change device region to United States
• Connect via VPN to United States
• Rewrite response status code for GET /v5/getstate server endpoint to 304 using a tool such as Charles Proxy
• Join rewards
• Wait until ads has initialized
• Attempt to view a targeted ad for a US subdivision such as US-OR (Oregon) [This is where the crash would occur]
• Quit the browser
• Remove the rewrite
• Launch the browser
• View a targeted ad for a US subdivision such as US-OR (Oregon)

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.

[emerick]

LGTM

[yachtcaptain23]

In general, should DoesRespectCap return false if the data is malformed? My impression, without insight in previous discussions, is that we should return true.

[tmancey]

If subdivision targeting has not been initialized we need to return false so that the ad is not shown outside of the intended region which is a part of the cap. Thanks

[moritzhaller]

lgtm!