Add escaping to quoted strings, differentiate between literal and
regular strings.
The goal is to make string processing in config files as close as
possible to toml standards. This means handing escape sequences
including unicode, and differentiating between literal strings and
regular strings in files and when splitting the command line. Also
allowing variable names in the files to be quoted.
This PR gets partway there. Removes some hacks from the previous PR to
deal with unusual option names and replaces with the quoted names.
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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
