Move contents of lib-dir to src-dir #477

Job	Run time
PHP-Linter (8.5) / linter	12s
Linter / json-linter	33s
Linter / yaml-linter	9s
PHP-Linter (8.4) / linter	12s
PHP-Linter (8.3) / linter	11s
Linter / style-linter	0s
Linter / ecmascript-linter	0s
Unit tests, PHP 8.3, windows-latest	4m 29s
Unit tests, PHP 8.5, ubuntu-latest	1m 53s
Unit tests, PHP 8.4, windows-latest	2m 13s
Unit tests, PHP 8.5, windows-latest	2m 16s
Unit tests, PHP 8.4, ubuntu-latest	35s
Unit tests, PHP 8.3, ubuntu-latest	28s
Code coverage	8s
Quality control	31s
Security checks	25s
Cleanup artifacts	6s
	14m 21s

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