Pull ICU, rename component build GN variables.
This ICU roll only renames component_mode -> is_component_build
Update other users of the component_mode string to is_component_build.
Rename the declaration to be local to BUILDCONFIG.gn (prefixed with '_').
Removes a bitrotted GN unit test around component handing (it wasn't
testing anything useful any more since we removed the built-in
component function).
Review URL: https://codereview.chromium.org/1275583002
Cr-Commit-Position: refs/heads/master@{#342204}
7 files changed
