Support PHP 7.4-8.5

[TomasVotruba]

Make swiss-knife installable and runnable on PHP 7.4 through 8.5, following the same native-7.4 approach as rectorphp/jack#47 (no scoper/PHAR build).

Source

• Downgraded src and bin to PHP 7.4 syntax (readonly to @readonly docblocks, typed class constants to plain constants, constructor promotion expanded, #[Override] removed, str_starts_with/str_contains rewritten, first-class callable rewritten). No new runtime dependency - all prod deps (entropy, nikic/php-parser) already support 7.4.
• composer.json: php constraint lowered to >=7.4.

Tests

• PHPUnit lowered to ^9.6 (runs the suite on the 8.4 analysis job); #[DataProvider] attributes converted to @dataProvider annotations; dropped the 10.x-only cacheDirectory from phpunit.xml.

CI

• bare_run.yaml now runs on push/PR across PHP 7.4, 8.2 and 8.5: installs prod dependencies, lints every src/bin file on the target version, and smoke-runs the binary.
• code_analysis.yaml keeps the full dev tooling on 8.4.

Closes the PHP 7.4-8.5 support work; the dependency floors were removed in #149, #150, #151, #152.