Add new `Performance/StringBytesize` cop #157

Job	Run time
Prism	34s
Ruby 2.7	38s
Check documentation syntax	9s
Ruby 3.0	34s
Check the oldest supported RuboCop version	43s
Ruby 3.1	36s
JRuby 9.4	2m 11s
Ruby 3.2	29s
Ruby 3.3	28s
Ruby head	29s
	6m 51s

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