Add endpoint for showing screenshots

[LiquidPL]

Depends on #12618.

Steps to deploy:

• Set cutoff screenshot ID for "legacy" screenshots without hash in the SCREENSHOTS_LEGACY_ID_CUTOFF env var.
• [OPTIONAL] Switch production to use these endpoints instead of legacy web if everything works correctly.

[LiquidPL]

that test did not fail on local >.<

[LiquidPL]

Time: 03:07.797, Memory: 253.00 MB

There was 1 error:

1) Tests\Controllers\ScreenshotsControllerTest
InvalidArgumentException: Unknown format "userName"

/home/runner/work/osu-web/osu-web/vendor/fakerphp/faker/src/Faker/Generator.php:743
/home/runner/work/osu-web/osu-web/vendor/fakerphp/faker/src/Faker/Generator.php:708
/home/runner/work/osu-web/osu-web/vendor/fakerphp/faker/src/Faker/Generator.php:973
/home/runner/work/osu-web/osu-web/vendor/fakerphp/faker/src/Faker/UniqueGenerator.php:76
/home/runner/work/osu-web/osu-web/database/factories/UserFactory.php:60
/home/runner/work/osu-web/osu-web/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Factories/Factory.php:507
/home/runner/work/osu-web/osu-web/vendor/laravel/framework/src/Illuminate/Collections/Arr.php:609
/home/runner/work/osu-web/osu-web/vendor/laravel/framework/src/Illuminate/Collections/Collection.php:799
/home/runner/work/osu-web/osu-web/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Factories/Factory.php:505
/home/runner/work/osu-web/osu-web/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Factories/Factory.php:447
/home/runner/work/osu-web/osu-web/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Factories/Factory.php:431
/home/runner/work/osu-web/osu-web/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Concerns/GuardsAttributes.php:155
/home/runner/work/osu-web/osu-web/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Factories/Factory.php:430
/home/runner/work/osu-web/osu-web/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Factories/Factory.php:404
/home/runner/work/osu-web/osu-web/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Factories/Factory.php:300
/home/runner/work/osu-web/osu-web/tests/Controllers/ScreenshotsControllerTest.php:21

seems like some issue with faker? i rerun the tests locally ensuring my composer deps are fully up to date, and it ran just fine. turns out faker really did not like being used inside setUpBeforeClass