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 empty-range check causes more bugs than it fixes. Replace it with
an explicit check for =NULL (see #7852).
Fixes#9311.
Fixes#9290.
Tests: unit (dev), cql-pytest on Cassandra 4.0
Signed-off-by: Dejan Mircevski <dejan@scylladb.com>
Closes#9314
