cat: Improve performance of formatting. #7007

Job	Run time
Style/spelling (ubuntu-latest, feat_os_unix)	1m 52s
Style/format (ubuntu-latest, feat_os_unix)	15s
Style/toml	10s
Style/lint (windows-latest, feat_os_windows)	2m 6s
Style/lint (macos-latest, feat_os_macos)	41s
Style/lint (ubuntu-latest, feat_os_unix)	41s
Style/Python	5s
	5m 50s

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