Micro-optimize `NamePrettifier::prettifyTestMethodName()` #754

Job	Run time
Coding Guidelines	44s
Dependency Validation	9s
Unit Tests (ubuntu-latest, 8.2)	13s
Type Checker	32s
Unit Tests (ubuntu-latest, 8.3)	10s
Unit Tests (ubuntu-latest, 8.4)	11s
Unit Tests (windows-latest, 8.2)	37s
Unit Tests (windows-latest, 8.3)	32s
Unit Tests (windows-latest, 8.4)	31s
End-to-End Tests (ubuntu-latest, 8.2)	44s
End-to-End Tests (ubuntu-latest, 8.3)	37s
End-to-End Tests (ubuntu-latest, 8.4)	42s
End-to-End Tests (windows-latest, 8.2)	1m 44s
End-to-End Tests (windows-latest, 8.3)	1m 41s
End-to-End Tests (windows-latest, 8.4)	1m 39s
Code Coverage	1m 24s
Build PHAR	27s
Test PHAR (8.2, pcov)	16s
Test PHAR (8.2, xdebug)	31s
Test PHAR (8.3, pcov)	21s
Test PHAR (8.3, xdebug)	30s
Test PHAR (8.4, pcov)	26s
Test PHAR (8.4, xdebug)	33s
	15m 14s

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