Move BraveConstants.java from org.chromium.chrome.browser.util to org.chromium.chrome.browser to align with upstream's hierarchy. Upstream's analogous ChromeStringConstants lives directly under org.chromium.chrome.browser, and the util package is treated as deprecated for new top-level constants/utilities. No behavior changes — pure refactor. Resolves: https://github.com/brave/brave-browser/issues/55685