csplit: use VecDeque instead of Vec for FIFO buffer #9446

Job	Run time
L10n/French Integration Test	1m 3s
L10n/Clap Error Localization Test	1m 2s
L10n/Fluent Syntax Check	19s
L10n/Installation Test (Make & Cargo) (macos-latest, feat_os_macos)	6m 29s
L10n/Multi-call Binary Install Test (macos-latest, feat_os_macos)	3m 23s
L10n/Installation Test (Make & Cargo) (ubuntu-latest, feat_os_unix)	4m 25s
L10n/Build and Test (windows-latest, feat_os_windows)	6m 3s
L10n/Locale Embedding - Cargo Install	48s
L10n/Multi-call Binary Install Test (ubuntu-latest, feat_os_unix)	3m 28s
L10n/Build and Test (macos-latest, feat_os_macos)	2m 36s
L10n/Build and Test (ubuntu-latest, feat_os_unix)	2m 34s
L10n/Locale Embedding - Multicall Binary	2m 1s
L10n/Locale Support Verification	6m 12s
L10n/Locale Embedding - Ls Utility	46s
L10n/Embedded Locale Regression Test	1m 7s
L10n/Locale Embedding - Cat Utility	40s
L10n/Locale Embedding Regression Test	3s
	42m 59s

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