This change introduces install_static::InstallDetails, a module-global
holder of details relating to the current install. It also more clearly
defines the concept of a primary install mode and one or more secondary
install modes (e.g., "Chrome SxS" for Google Chrome's canary channel).
Furthermore, it creates a clear boundary for brand-specific constants so
that Chromium and Google Chrome don't bleed into one another. See
chrome/install_static/README.md for more information.

BUG=373987
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.win:win10_chromium_x64_rel_ng

Review-Url: https://codereview.chromium.org/2422643002
Cr-Commit-Position: refs/heads/master@{#430728}