Simplify _getUntitledFileSuggestion and its caller
Add support for normalizing UNC paths in the FileSystem, controlled by the FileSystemImpl.normalizeUNCPaths flag
Increase untitled document limit to 9999 and fix ternary operator formatting.
Rename the duplicated-slash regular expression and add JSDoc
Merge pull request #5984 from adobe/iwehrman/simplify-getUntitledFileSuggestion

Simplify _getUntitledFileSuggestion
Assume the FileSystem is initialized within `_normalizePath`; initialize the singleton instance at module load
Merge pull request #6041 from adobe/iwehrman/normalize-UNC-paths

Correctly normalize UNC paths