Implement Query Directory Parsing

[goodwillpunning]

Currently, parsing a local directory for query files remains a marked TODO item in the source code. The logic for this feature is as follows:

• If a local directory is provided either as a parameter to the Benchmark constructor or explicitly set using the .setQueryDir() function, then
• All files in the local directory should be listed
• All files in the local directory should be filtered to include only files with a .sql extension
• The filtered list of files should be parsed into a global list of queries and headers
• The headers should be validated to be unique across the entire set