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 wasm::engine exists as a sharded<> service in main, but it's only
passed by local reference into database on start. There's no much profit
in keeping it at main scope, things get much simpler if keeping the
engine purely on database.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
