* Restore legacy unique_keys[] support in the schema API
develop expresses a unique index as a `keys[]` entry with `'unique' => true`,
and both db_table_create() and db_update_table() were rewritten to only read
that form. Plugins that still use the legacy `unique_keys[]` definition style
(supported on 1.2.x) therefore get no UNIQUE index created, and any existing
one dropped on the next schema refresh.
Fold a legacy `unique_keys[]` definition into `keys[]` with the unique flag at
the top of both functions, so the existing unique-aware key handling applies
to it. New-style `keys[]` with `'unique' => true` continues to work unchanged.
* CHANGELOG: reference PR #8116
* Fix CHANGELOG format and add unique_keys[] regression coverage
CHANGELOG: use the -issue#8116 entry form (the -bug prefix and trailing (#NNNN) failed the CHANGELOG format check) and place it in the issue block so the security-issue-feature ordering holds. Adds DbUpdateTableUniqueKeysTest covering db_table_create() emitting the UNIQUE index and db_update_table() adding a missing one and preserving an existing one for a legacy unique_keys[] definition. FakeMySQLPDO now projects Seq_in_index/Column_name/Non_unique for named secondary indexes so the reconciliation path can be exercised.
TheWitness