Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
The view update backlog represents the pending view data that a base replica
maintains. It is the maximum of the memory backlog - how much memory pending
view updates are consuming - and the disk backlog - how much view hints are
consuming. The size of a backlog is relative to its maximum size.
We will use this class to represent a base replica's view update
backlog at the coordinator.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>