Building on #3311, which started moving the result string into a
`unique_ptr`, instead have `StringLiteral` use a `BumpPtrAllocator` to
manage memory. But also, detect when a string is really trivial during
`Lex` and, if so, return `contents_` directly.
Continuing with #3070. Just a dir and file rename (only prefix change is
lexer_file_test). Everything in the lex dir should be marked as a move.
Note, I think this closes#3070. There may still be further cleanup
later, but the organizational changes suggested there are being
completed.
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Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Jon Ross-Perkins
