Use first-class callable syntax

Promote all remaining string-based callables to first-class callable
syntax. See smrealms#1183.

This refactoring was performed with rector.

rector.php

@@ -1,10 +1,12 @@
 <?php declare(strict_types=1);
 
 use Rector\Config\RectorConfig;
+use Rector\Php81\Rector\Array_\FirstClassCallableRector;
 
 return static function (RectorConfig $rectorConfig): void {
 	$rectorConfig->paths([
 		__DIR__ . '/test',
 		__DIR__ . '/src',
 	]);
+	$rectorConfig->rule(FirstClassCallableRector::class);
 };

src/lib/Smr/Discord/Commands/Turns.php

@@ -2,8 +2,8 @@
 
 namespace Smr\Discord\Commands;
 
+use Smr\AbstractPlayer;
 use Smr\Discord\DatabaseCommand;
-use Smr\Player;
 
 class Turns extends DatabaseCommand {
 
@@ -16,10 +16,10 @@ public function description(): string {
 	}
 
 	public function databaseResponse(string ...$args): array {
-		return array_map([$this, 'getTurnsMessage'], $this->player->getSharingPlayers(true));
+		return array_map($this->getTurnsMessage(...), $this->player->getSharingPlayers(true));
 	}
 
-	private function getTurnsMessage(Player $player): string {
+	private function getTurnsMessage(AbstractPlayer $player): string {
 		// turns only update when the player is active, so calculate current turns
 		$turns = min(
 			$player->getTurns() + $player->getTurnsGained(time(), true),

src/lib/Smr/Request.php

@@ -119,14 +119,14 @@ public static function get(string $index, string $default = null): string {
 	 * Note that this does not save the result in $var (see Smr\Session).
 	 */
 	public static function getVar(string $index, string $default = null): string {
-		return self::getVarX($index, $default, [self::class, 'get']);
+		return self::getVarX($index, $default, self::get(...));
 	}
 
 	/**
 	 * Like getVar, but returns an int instead of a string.
 	 */
 	public static function getVarInt(string $index, int $default = null): int {
-		return self::getVarX($index, $default, [self::class, 'getInt']);
+		return self::getVarX($index, $default, self::getInt(...));
 	}
 
 	/**
@@ -136,7 +136,7 @@ public static function getVarInt(string $index, int $default = null): int {
 	 * @return array<int>
 	 */
 	public static function getVarIntArray(string $index, array $default = null): array {
-		return self::getVarX($index, $default, [self::class, 'getIntArray']);
+		return self::getVarX($index, $default, self::getIntArray(...));
 	}
 
 	/**