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 main user of this list is MVCC implementation in partition_version.cc.
The reason why boost::intrusive::list<> cannot be used is that tere is no
single owner of the list who could keep boost::intrusive::list<> object
alive. In the MVCC case there is at least one partition_entry object and
possibly multiple partition_snapshot objects which lifetime is independent
and the list must remain in a valid state as long as at least one of them
is alive.
Signed-off-by: Paweł Dziepak <pdziepak@scylladb.com>
