Extend base::Callback to have a move-only variant

Add CopyMode flag to base::Callback to split it to the copyable variant
and the move-only variant.

BUG=554299

Review URL: https://codereview.chromium.org/1699773002

Cr-Commit-Position: refs/heads/master@{#380108}
5 files changed