cat: Improve performance of formatting. #7010

Job	Run time
Style/spelling (ubuntu-latest, feat_os_unix)	1m 8s
Style/format (ubuntu-latest, feat_os_unix)	20s
Style/lint (macos-latest, feat_os_macos)	44s
Style/toml	12s
Style/lint (ubuntu-latest, feat_os_unix)	48s
Style/lint (windows-latest, feat_os_windows)	2m 2s
Style/Python	5s
	5m 19s

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