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
Add additional comments to select_statement_utils, fix formatting, add
missing #pragma once and introduce set_internal_paging_size_guard to
set internal_paging in RAII fashion.
Closes#7507
Before this change, internal page_size when doing aggregate, GROUP BY
or nonpaged filtering queries was hard-coded to DEFAULT_COUNT_PAGE_SIZE.
This made testing hard (timeouts in debug build), because the tests had
to be large to test cases when there are multiple internal pages.
This change adds new internal_paging_size variable, which is
configurable by set_internal_paging_size and reset_internal_paging_size
free functions. This functionality is only meant for testing purposes.
