fix(date): treat composite strftime specifiers as atomic #12319

Job	Run time
L10n/Embedded Locale Regression Test	1m 43s
L10n/Fluent Syntax Check	18s
L10n/Build and Test (macos-latest, feat_os_unix)	3m 41s
L10n/Installation Test (Make & Cargo) (ubuntu-latest, feat_os_unix)	7m 1s
L10n/Locale Embedding - Cat Utility	46s
L10n/Multi-call Binary Install Test (macos-latest, feat_os_unix)	3m 47s
L10n/Locale Support Verification	7m 41s
L10n/Installation Test (Make & Cargo) (macos-latest, feat_os_unix)	8m 13s
L10n/Locale Embedding - Cargo Install	49s
L10n/Clap Error Localization Test	1m 38s
L10n/Multi-call Binary Install Test (ubuntu-latest, feat_os_unix)	4m 18s
L10n/Locale Embedding - Ls Utility	1m 18s
L10n/Locale Embedding - Multicall Binary	2m 56s
L10n/Build and Test (windows-latest, feat_os_windows)	6m 25s
L10n/Build and Test (ubuntu-latest, feat_os_unix)	3m 18s
L10n/French Integration Test	1m 39s
	55m 31s

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