Problem: Several string utilities return or store views into their input.
A temporary std::string can leave these views dangling, although no current caller does this.
Fix: Add LIFETIMEBOUND so Clang diagnoses the misuse while preserving immediate use.
Pass the Split span by value so lvalue strings do not trigger false warnings.
The string-view helpers return views into their input, while `LineReader` stores one.
Annotate their inputs so Clang can warn when a returned or stored view outlives a temporary string.
`Split` can return views into its input, but annotating its old reference warns for lvalue strings.
Take the span by value so Clang follows the backing storage.
`Split<std::string>` copies results but can still warn, while `SplitString` is unaffected.
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For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/36164.
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