Add plugin migration system

- Add `runPendingMigrations()` to `PluginManager` for executing plugin-specific migrations.
- Create `PluginMigrationModel` for managing plugin migration versions.
- Add migration for creating the `plugin_migrations` table to track migration states.

Signed-off-by: objec <objecttothis@gmail.com>

app/Database/Migrations/sqlscripts/3.5.1_PluginMigrationsTableCreate.sql

@@ -0,0 +1,6 @@
+CREATE TABLE IF NOT EXISTS `ospos_plugin_migrations` (
+    `plugin_id` varchar(100) NOT NULL,
+    `version`   bigint(20) UNSIGNED NOT NULL DEFAULT 0,
+    `ran_at`    datetime NOT NULL DEFAULT current_timestamp() ON UPDATE current_timestamp(),
+    PRIMARY KEY (`plugin_id`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;