[CodeHealth] Enable `-Wunsafe-buffer-usage` acrosss brave This PR removes `brave/` from the blanket exclusion for `-Wunsafe-buffer-usage`, and adds only certain third party subpaths to it. Additionally, in order correct the ensuing warning violations, this PR adds to individual files exclusion annotations, that we can revisit gradually. Having this warning on will prevent further violations from popping up in new places in the codebase. A significant amount of effort has already been employed in correcting some of these unsafe buffer usages. For reference: https://chromium.googlesource.com/chromium/src/+/refs/heads/main/docs/unsafe_buffers.md Resolves https://github.com/brave/brave-browser/issues/41660