Added ability to request db versio, table engines + group requirements with 'one_of' condition

[SergeR]

Database requirements:

[
  'db' => ['server'=>'MySQL, MariaDB', 'engine'=>'InnoDB'],
  'db.mysql' => ['version' => '>=5.6.4'],
  ['db.mariadb', ['version' => '>=10']
]

Group requirements

Testing is passed if at least one requirement item is passed testing

[
  [
    ['php', 'version' => '>=7.4'],
    ['php', 'version' => '<8.1']
  ],

  'one_of' => [
    'db.mysql' => ['version' => '>=8'],
    'db.mariadb' => ['version' => '>=10.1']
  ]
]

[SergeR]

I put together a small PHPUnit suite covering testDb() and the new one_of grouping (pass-if-any-alternative, fail-if-all-fail, short-circuit on first pass). It's not part of this PR's diff since the framework has no official test setup - shared as a gist instead, meant purely as a way to verify the behavior locally, not a proposal to add PHPUnit/Composer to the repo:

https://gist.github.com/SergeR/8b76904f47b72c91f519e571e372b39d

The gist's README has full install/run instructions; short version:

1. Drop the files into a local tests/ folder at the repo root (layout is in the README).
2. cd tests/vendors/phpunit && ./download.sh - fetches a gitignored phpunit-9.phar, nothing committed.
3. php tests/vendors/phpunit/phpunit.phar -c tests/phpunit.xml runs the non-DB tests (8 tests, no setup needed).
4. DB-dependent tests (testDb, one_of across DB servers) are excluded by default; run them with --group db after pointing wa-config/db.php at a throwaway database.

Happy to adjust the test cases if there's a preferred format/location for tests in this repo going forward.