fix: Ensure that callback definitions are not converted into closures…

[tweis]

…, as closures can break the rendering of the configuration module in the TYPO3 backend

[github-actions]

TYPO3 v12.4 tests on PHP 8.2

Code Coverage
Package	Lines		Functions		Classes		Health
netlogix/nximageoptimizer	42.70%	38/89	77.78%	7/9	60.00%	3/5	➖
Summary	42.70%	38/89	77.78%	7/9	60.00%	3/5	➖

[github-actions]

TYPO3 v12.4 tests on PHP 8.1

Code Coverage
Package	Lines		Functions		Classes		Health
netlogix/nximageoptimizer	42.70%	38/89	77.78%	7/9	60.00%	3/5	➖
Summary	42.70%	38/89	77.78%	7/9	60.00%	3/5	➖

[github-actions]

TYPO3 v12.4 tests on PHP 8.3

Code Coverage
Package	Lines		Functions		Classes		Health
netlogix/nximageoptimizer	42.70%	38/89	77.78%	7/9	60.00%	3/5	➖
Summary	42.70%	38/89	77.78%	7/9	60.00%	3/5	➖