Add new `Performance/StringBytesize` cop #159

Job	Run time
Check documentation syntax	26s
JRuby 9.4	2m 44s
Ruby 2.7	57s
Prism	53s
Check the oldest supported RuboCop version	1m 1s
Ruby 3.0	44s
Ruby 3.1	50s
Ruby 3.2	42s
Ruby 3.3	54s
Ruby head	47s
	9m 58s

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