[db] Move get_long from DB_BASE to DB_CONN
Fixes #6972
Description of the Change
Move arbitrary scalar integer queries to DB_CONN alongside get_double. Update DB_BASE::max_id and DB_BASE::count to use their connection, keeping their public behavior and the scalar conversion unchanged.
Alternate Designs
Move the existing implementation rather than adding a second query helper or retaining table-specific ownership.
Release Notes
N/A
Validation
- Repository source-code and trailing-whitespace checks passed.
git diff --checkpassed.- Repository call sites were checked for references to the moved method. Autotools generation, server configuration, and make -j2 -C db passed in a Debian container. A complete server build and live database integration test have not been verified.
AI assistance
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Summary by cubic
Fixes #6972. Moves get_long from DB_BASE to DB_CONN so arbitrary scalar integer queries live alongside get_double. Updates DB_BASE::max_id and DB_BASE::count to call db->get_long, preserving their public behavior. get_long is no longer available on DB_BASE; any external callers must use db->get_long instead.