This adds the following functions to `cmStringAlgorithms`:
- `cmIsSpace`
- `cmTrimWhitespace` (moved from `cmSystemTools::TrimWhitespace`)
- `cmEscapeQuotes` (moved from `cmSystemTools::EscapeQuotes`)
- `cmTokenize` (moved from `cmSystemTools::tokenize` and adapted to
accept `cm::string_view`)