Declare classes readonly #3325

Job	Run time
Coding Guidelines	36s
Dependency Validation	21s
Static Analysis	42s
Unit Tests (ubuntu-latest, 8.2)	49s
Unit Tests (ubuntu-latest, 8.3)	14s
Unit Tests (ubuntu-latest, 8.4)	13s
Unit Tests (ubuntu-latest, 8.5)	12s
Unit Tests (windows-latest, 8.2)	43s
Unit Tests (windows-latest, 8.3)	36s
Unit Tests (windows-latest, 8.4)	33s
Unit Tests (windows-latest, 8.5)	34s
End-to-End Tests (ubuntu-latest, 8.2)	49s
End-to-End Tests (ubuntu-latest, 8.3)	51s
End-to-End Tests (ubuntu-latest, 8.4)	53s
End-to-End Tests (ubuntu-latest, 8.5)	44s
End-to-End Tests (windows-latest, 8.2)	1m 47s
End-to-End Tests (windows-latest, 8.3)	1m 55s
End-to-End Tests (windows-latest, 8.4)	2m 7s
End-to-End Tests (windows-latest, 8.5)	1m 58s
Build PHAR	29s
Code Coverage	3m 0s
Test PHAR (8.2, pcov)	36s
Test PHAR (8.2, xdebug)	38s
Test PHAR (8.3, pcov)	21s
Test PHAR (8.3, xdebug)	34s
Test PHAR (8.4, pcov)	17s
Test PHAR (8.4, xdebug)	37s
Test PHAR (8.5, pcov)	22s
Test PHAR (8.5, xdebug)	31s
	24m 2s

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